Color filter for liquid crystal display and semitransmission liquid crystal display

ABSTRACT

The present invention provides a low-cost transflective liquid crystal display exhibiting high color reproducibility in a transmissive display and excellent characteristics (color reproducibility and brightness) in a reflective display. Also, the present invention provides a color filter for a bright transflective liquid crystal display. 
     The transflective liquid crystal display includes a pair of substrates disposed opposite to each other with a liquid crystal layer held therebetween, a reflection means using ambient light as a light source, and a backlight source. The transflective liquid crystal display further includes a color filter having a transmissive region and a reflective region which are provided in each picture element of the color filter and which have colored layers comprising a single material, and a three-peak type LED backlight source.

TECHNICAL FIELD

The present invention relates to a color filter for a liquid crystaldisplay and a transflective display using the same.

BACKGROUND ART

Liquid crystal displays are now used for various applications such asnotebook-size PC, mobile terminals, desktop monitors, digital cameras,and the like by making use of the characteristics of the liquid crystaldisplays, such as light weight, thinness, low power consumption, and thelike. In order to further decrease the power consumption of a liquidcrystal display using a backlight, the utilization efficiency of thebacklight must be improved. Therefore, a color filter is required tohave improved transmittance. Although the transmittance of the colorfilter is being improved every year, a significant decrease in powerconsumption is not expected from improvement in transmittance.

In recent years, the development of a reflective liquid crystal displaynot requiring a backlight source having high power consumption has beenadvanced, and it has been reported that the power consumption can bedecreased to about 1/7 of that of a transmissive liquid crystal display(Nikkei Macrodevice, separate volume, Flat Panel Display, 1998, P. 126).

A reflective liquid crystal display has the advantage of low powerconsumption and excellent outdoor visibility. However, in a place wheresufficient environment light cannot be secured, a display becomes dark,thereby causing. the problem of significantly deteriorating visibility.In order to make a display visible in a place where environmental lighthas low strength, two systems each comprising-a light source have beendesigned. One of the systems is (1) a liquid crystal display, i.e., aso-called transflective liquid crystal display, comprising a backlightas a light source and a reflection layer provided in each pixel andhaving a notch so that the a part of the reflection layer is used for atransmissive display system, and a part of the reflection layer is usedfor a reflective display system (refer to documents such as Fine ProcessTechnology Japan '99, Expert Technology Seminar Text A5). The othersystem is (2) a reflective liquid crystal display comprising a frontlight.

As each of a backlight source and a front light source used for mobileterminals, a three-peak type fluorescent lamp or a white LED (lightemitting diode) is used. The three-peak type fluorescent lamp isadvantageous from the viewpoint of power consumption, and thisfluorescent lamp is known to improve the color reproducibility oftransmitted color light. Thus, the three-peak fluorescent lamp is usedfor relatively large mobile terminals such as a mobile PC, PDA, and thelike. On the other hand, a white LED is advantageous for a smaller sizeand thickness and is used for small mobile terminals such as a cellularphone and the like.

White LEDs are divided into a two-peak type and a three-peak typeaccording to the spectral shapes. The two-peak type white LED uses acombination of a blue LED and a phosphor, for obtaining a white color(FIG. 5). On the other hand, the three-peak type white LED uses acombination of an ultraviolet LED and red, green and blue phosphors(FIG. 1), or a combination of LEDs of the three colors, i.e., red, greenand blue (FIG. 2), for obtaining a white color. The two-peak type whiteLED has been used as an option of the white LED light source so far(Nikkei Electronics, 2002, No. 2-25).

A transflective display comprising a backlight comprises pictureelements in each of which a transmissive display using backlight and areflective display using environmental light coexist, and thus a displaywith excellent visibility can be achieved regardless of the strength ofenvironmental light. However, in the use of such a conventional colorfilter as shown in FIG. 6, i.e., a color filter in which a reflectiveregion and a transmissive region are not provided in each pictureelement to cause uniform color characteristics within each pictureelement, a problem occurs in producing a vivid transmissive display.More specifically, when the color vividness (color purity) oftransmitted color light is improved, the color purity of reflected colorlight is also further increased to significantly decrease brightnesshaving a trade-off relation to color purity. Therefore, sufficientvisibility cannot be obtained for reflective display. This problem isdue to the fact that in the transmissive display, backlight istransmitted once through the color filter, while in the reflectivedisplay, environmental light is transmitted through the color filter twotimes-including the time of incidence and the time of reflection. In thetransmissive display, the backlight is used as a light source, while inthe reflective display, natural light is used as a light source.Therefore, the transmissive display and reflective display are differentin not only color purity but also color tone. This is due to the factthat natural light has a continuous spectrum like the spectrum of lightsource D65 shown in FIG. 13, while the backlight source has spectralpeaks at characteristic wavelengths, as shown in FIGS. 1 to 5.

A method for solving the above problem is a method in which atransparent resin layer is formed in each reflective region to thin acolored layer in each reflective region, thereby improving thebrightness of a reflective display. This method is a so-called thicknesscontrolling method and disclosed in Japanese Unexamined PatentApplication Publication No. 2001-33778. FIG. 7 schematically shows across-section of a conventional color filter for a transflective liquidcrystal display. A transparent resin layer 3 is formed in eachreflective region 6 to decrease the thickness of a colored layer 5 ineach reflective region 6, as compared with the thickness of the coloredlayer 5 in each transmissive region 7. In order that the colored layerin each reflective region has the same degree of brightness as that ofthe colored layer in each transmissive region, the thickness of thecolored layer in each reflective region must be set to ½ or less of thethickness of the colored layer in each transmissive region. On the otherhand, an increase in the degree of thinning of the colored layer in eachreflective region causes large variations in the thickness, i.e., largevariations in display colors, thereby causing a manufacture problem suchas a reduction in yield, or the like. In consideration of processabilityand improvement in the brightness of the reflective display, thethickness of the colored layer in each reflective region must be set toabout ½ to ⅖ of the thickness of the colored layer in each transmissiveregion. In this method for improving the color reproducibility in thetransmissive display, with the above-described degree of thinning,sufficient brightness cannot be obtained in the reflective display,thereby causing the problem of failing to satisfy both a vividtransmissive display and a bright reflective display. Also, the problemin which the transmissive display and the reflective display havedifferent color tones cannot be solved only by changing the thickness.

In the use of a color filter in which a transmissive region and areflective region is coated separately, as shown in FIG. 8, color purityand brightness can be freely changed, thereby achieving a transmissivedisplay color and brightness, and a reflective display color andbrightness adequate for the purpose. In this method (six-color coatingmethod), the color layers of the reflective regions are independent ofthose of the transmissive regions, and thus the reflective display withsufficient brightness can be achieved even when the colorreproducibility of the transmissive display is increased. However, in aphotolithography method which is a main stream at present, coating of acoloring agent and photolithography process are performed two times ormore for forming picture elements of one color, and thus two lithographyprocesses for each color, i.e., a total of six photolithographyprocesses, are required for forming the picture elements of the threecolors including red, green and blue, thereby causing the problem ofincreasing the manufacturing cost. When a coloring agent is coated inthe transmissive regions (or the reflective regions), and then acoloring agent is coated in the reflective regions (or the transmissiveregions), from the viewpoint of production, it is difficult to coat thecoloring agents in such a manner that no space occurs between thetransmissive regions and the reflective regions, and the coloring agentsdo not overlap with each other. Therefore, there is the possibility thatthe product yield is decreased to increase the manufacturing cost of thecolor filter. When spaces occur between the reflective regions and thetransmissive regions, light leaks from the spaces to decrease the imagequality of a liquid crystal display. On the other hand, when thecoloring agents overlap with each other, the color only at theboundaries is increased and is possibly recognized as ununiformity on ascreen. Furthermore, the cell gap of the liquid crystal display becomesdefective. Namely, the yield of the liquid crystal display deterioratesto possibly increase the manufacturing cost of the liquid crystaldisplay.

As a method capable of a transmissive display and reflective displaywith high color reproducibility, a method comprising forming an aperturein each reflective region to improve the brightness of the reflectivedisplay, i.e., an area controlling method, is disclosed in JapaneseUnexamined Patent Application Publication No. 2000-111902. FIG. 9schematically shows a cross-section of a conventionally known colorfilter for a transflective liquid crystal display having the apertures.In this case, only three times of photolithography processes areperformed to permit the manufacture of a color filter at low cost.However, this method decreases the color purity-reflectancecharacteristics of the reflective display, as compared with the methodin which the transmissive regions and the reflective regions are coatedseparately. Therefore, this method has the problem of failing to satisfyboth color vividness and sufficient brightness. Particularly, when thecolor reproducibility is increased in the transmissive display and thereflective display, the brightness of the reflective display isdecreased to cause the insufficient performance as a liquid crystaldisplay.

In a conventional transflective liquid crystal display such as a mobileterminal or the like a two-peak type LED light source or three-peak typefluorescent lamp is used. However, a combination with a conventionallyknown low-cost color filer for a transflective liquid crystal displayhas the problem of failing to achieve a level in which both the highcolor reproducibility of the transmissive display and the sufficientbrightness of the reflective display are satisfied.

DISCLOSURE OF INVENTION

The present invention has been achieved in consideration of the aboveproblems, and an object of the present invention is to provide alow-cost transflective liquid crystal display capable of a transmissivedisplay having high color reproducibility and a reflective displayhaving excellent characteristics (color reproducibility and brightness).Another object of the present invention is to provide a color filter atlow cost, which is capable of removing a difference in chromaticitybetween a reflective display and a transmissive display of atransflective liquid crystal display to exhibit excellent colorcharacteristics and display characteristics.

The problems of the prior art can be resolved by the followingrequirements.

(1) A transflective liquid crystal display comprises a pair ofsubstrates disposed opposite to each other with a liquid crystal layerheld therebetween, a reflection means using ambient light as a lightsource, a backlight source, and a color filter having a transmissiveregion and a reflective region which are provided in each pictureelement of the color filter and which have colored layers comprising asingle material, a three-peak type LED backlight source being used asthe backlight source.

(2) The color filter used in the transflective liquid crystal display(1) includes the picture elements at least one color in each of whichthe transmissive region and the reflective region comprise therespective colored layers having the same thickness, and the reflectiveregion has an aperture.

(3) The color filter used in the transflective liquid crystal display(1) includes the picture elements of at least one color in each of whichthe colored layers in the reflective region and the transmissive regionhave different thicknesses.

(4) The color filter used in that transflective liquid crystal layer (3)has the aperture formed in each reflective region.

(5) A color filter for a liquid crystal display comprises transmissiveregions and reflective regions, wherein at least two types of coloredlayers are deposited in the transmissive region of each of pictureelements of at least one color.

(6) In the color filter (5) for a liquid crystal display, a firstcolored layer is deposited in each transmissive region, and a secondcolored layer is deposited on the first colored layer and in eachreflective region.

(7) In the color filter (5) for a liquid crystal display, a firstcolored layer is deposited in each of the transmissive regions and thereflective regions, and a second colored layer is deposited on the firstcolored layer in each transmissive region.

(8) In the color filter (5) for a liquid crystal display, thetransmissive region and the reflective region in each of the pictureelements of at least one color comprise a single coloring agent, andeach reflective region has a transparent region.

(9) In the color filter (5) for a liquid crystal display, green coloredlayers having different pigment compositions are laminated.

(10) In the color filter (5) for a liquid crystal display, red coloredlayers having different pigment compositions are laminated.

(11) In the color filter (10) for a liquid crystal display, a redcolored layer containing a pigment having a quinacridone skeleton islaminated on another colored layer. (12) In the color filter (5) for aliquid crystal display, blue colored layers having different pigmentcompositions are laminated.

(13) In the color filter (5) for a liquid crystal display, a singlecolored layer is laminated on the blue colored layer and the red coloredlayer so that the area of a coloring agent laminated on the blue coloredlayer is smaller than that laminated on the red colored layer.

(14) In the color filter (5) for a liquid crystal display, an over coatlayer is deposited on the colored layers.

(15) The color filter (5) for a liquid crystal display does not containa picture element having a chromaticity difference δ satisfying thefollowing relation between transmissive region chromaticity (x0, y0) andreflective region chromaticity (x, y):δ=(x−x0)²+(y−y0)²≧1×10⁻³

(16) A transflective liquid crystal display comprises the color filter(5).

Although the three-peak type light source is known to improve colorreproducibility of a transmissive display, in the present invention, itwas found that the three-peak type light source may improve not only thecolor characteristics of a transmissive display but also the colorcharacteristics of a reflective display using environmental light. In aspecified color filter structure, i.e., an area controlling system orthickness controlling system, the color characteristics can be improved.It was also found that in the use of a LED light source as thethree-peak type light source, the characteristics of the reflectivedisplay can be significantly improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a chart showing an example (ultraviolet LED+red, green andblue phosphors) of the spectrum of a three-peak type light source usedin the present invention;

FIG. 2 is a chart showing an example (combination of red, green and blueLEDs) of the spectrum of a three-peak type light source used in thepresent invention;

FIG. 3 is a chart showing an example of the spectrum of a three-peaktype cold cathode fluorescent lamp;

FIG. 4 is a chart showing an example of the spectrum of a three-peaktype organic electroluminescence light source;

FIG. 5 is a chart showing an example of the spectrum of a two-peak typeLED light source;

FIG. 6 is a drawing showing the configuration of a color filter used ina transflective liquid crystal display;

FIG. 7 is a drawing showing the configuration of a color filter used ina transflective liquid crystal display;

FIG. 8 is a drawing showing the configuration of a color filter used ina transflective liquid crystal display;

FIG. 9 is a drawing showing the configuration of a color filter used ina transflective liquid crystal display;

FIG. 10 is a chart showing a spectrum of a transmissive region in eachof Examples 1 and 5 (combination with a three-peak type LED) and aspectrum of a transmissive region in Comparative Example 1 (combinationwith a two-peak type LED);

FIG. 11 is a chart showing a spectrum of a reflective region in Example1 (combination of an area-controlling system color filter and athree-peak type LED);

FIG. 12 is a chart showing a spectrum of a reflective region in Example5 (combination of a thickness-controlling system color filter and athree-peak type LED);

FIG. 13 is a chart showing the spectra of standard light source C andlight source D65;

FIG. 14 is a drawing showing the configuration of a color filter ofExample 11;

FIG. 15 is a drawing showing the configuration of a color filter ofExample 12;

Reference numeral 1 denotes a transparent substrate; reference numeral2, a black matrix; reference numeral 3, a transparent resin layer;reference numeral 4, a colored layer comprising non-photosensitive colorpaste; reference numeral 5, a colored layer comprising a photosensitivecolor resist; reference numeral 6, a reflective region; referencenumeral 7, a transmissive region; reference numeral 8B, a blue pictureelement; reference numeral 8G, a green picture element; referencenumeral 8R, a red picture element; reference numeral 9, an apertureregion; and reference numeral 10, an over coat layer.

BEST MODE FOR CARRYING OUT THE INVENTION

A transflective liquid crystal display of the present inventioncomprises a liquid crystal layer having at least a light controllingfunction using an applied voltage, a pair of substrates disposedopposite to each other with the liquid crystal layer held therebetween,a reflection means using ambient light as a light source, and abacklight source.

In the liquid crystal display, it is important to provide a reflectionplate partially formed on a surface of the substrate apart from theobservation side, the surface of the substrate being in contact with theliquid crystal, a color filter having a transmissive region transmittinglight emitted from the backlight source and a reflective regionreflecting external light, which are provided in a region correspondingto one picture element of the color filter, and a three-peak type LEDbacklight source used as the backlight source disposed at the back ofthe substrate apart from the observation side. In the color filter, asingle colored layer is formed in each picture element, the transmissiveregion and the reflective region in each picture element have differentcolor characteristics.

By providing both the reflection means and the backlight source, a gooddisplay can be obtained even in an outdoor environment having strongambient light and in a relatively dark indoor environment. Also, thereflection means is disposed on the surface of the substrate apart fromthe observation side, the surface of the substrate being in contact withthe liquid crystal, thereby producing a clear image with neither blurdue to parallax and nor color mixing. Furthermore, the color filtercomprising the transmissive regions and the reflective regions havingdifferent color characteristics, and the three-peak type LED backlightsource are provided to permit the achievement of the transflectiveliquid crystal display with excellent visibility, which is capable ofperforming both a transmissive display with color vividness and a brightreflective display.

In the transflective liquid crystal display of the present invention,the substrate having the reflection means formed thereon may be thecolor filter substrate or the substrate apart from the color filter.When a reflection layer is formed on the color filter substrate, in eachpicture element having a coloring agent formed therein, each regionhaving the reflection layer formed therein is the reflective region, andeach region without the reflection layer is the transmissive region.When the reflection layer is formed on the substrate apart from thecolor filter, a color filter picture element region corresponding toeach region having the reflection layer of the substrate is thereflective region, and a color filter picture element regioncorresponding to each region without the reflection layer of thesubstrate is the transmissive region.

In the color filter used in the transflective liquid crystal display ofthe present invention, it is important that the transmissive regions andthe reflective regions have different color characteristics. From theviewpoint of low-cost manufacture of the liquid crystal display, thecolor filter may be a color filter, i.e., an area-controlling systemcolor filter, comprising picture elements of at least one color in eachof which the same colored layer is formed in the transmissive region andthe reflective region, and the reflective region has an aperture region,or a color filter, i.e., a thickness-controlling system color filter,comprising picture element of at least one color in each of which atransparent resin layer is disposed between the substrate and thecolored layer in the reflective region, and the colored layers of thereflective region and the transmissive region have differentthicknesses. A color filter using a combination of the area-controllingsystem and the thickness-controlling system within each picture elementmay be used. Alternatively, a color filter having a plurality of coloredlayers laminated in the transmissive region of one picture element maybe used. As the plurality of the colored layers, different coloredlayers or the same colored layer may be used.

The same colored layer means that a pigment composition and apigment-resin ratio by weight are the same, and the different coloredlayers mean that any one of the pigment composition and thepigment-resin ratio by weight is different.

In the color filter used in the present invention, all picture elementsneed not have the same color filter structure, and the picture elementshaving different color filter structures may be used.

In the color filter used in the present invention, the transmissiveregion and the reflective region in each of the picture elements of atleast one color may have the same colored layer and the same thickness,and an aperture region may be formed in the reflective region. Byforming the aperture region in each reflective region, the brightness ofeach reflective display can be improved, and the manufacturing cost canbe decreased. The color of the regions having the aperture regions isnot particularly limited, and the aperture regions may be formed in thepicture elements of any one of red, green, and blue. However, inconsideration of a characteristic difference between the black lightsource and environmental light, the color of the picture elements ineach of which the aperture region is formed, and the ratio (referred toas an “aperture region ratio”) of the aperture regions to the reflectiveregions are preferably determined to achieve target colorcharacteristics and brightness. Specifically, the aperture region meansa region in which the average transmittance in the visible region is 80%or more.

When the aperture regions are formed in the picture elements of aplurality of colors, the aperture region ratios are preferably set inthe order of green>red¢blue. The aperture region ratio of the redpicture element is substantially the same as that of the blue pictureelement. More specifically, the aperture region ratio of the greenpicture elements is preferably 10% to 50%, the aperture region ratio ofthe red picture elements is preferably 5% to 30%, and the apertureregion ratio of the blue picture elements is preferably 30% or less.More preferably, the aperture region ratio of the green picture elementsis 10% to 40%, the aperture region ratio of the red picture elements is6% to 25%, and the aperture region ratio of the blue picture elements is4% to 25%. When each of the aperture region ratios is smaller than theabove range, a bright reflective display cannot be obtained, while eachof the aperture region ratios is larger than the above range, areflective display with color vividness cannot be obtained.

When the formation of the aperture regions deteriorates surface flatnessto possibly disturb liquid crystal alignment, an over coat layer ispreferably formed as a planarizing layer on the coloring agents.Examples of the over coat layer include an epoxy resin layer, an acrylepoxy resin layer, an acryl resin layer, a siloxane polymer layer, apolyimide layer, a silicon-containing polyimide layer, apolyimidosiloxane layer, and the like.

In the color filter used in the present invention, a transparent resinlayer may be formed in the reflective region of each of the pictureelements of at least one color on the substrate.

When the transparent resin layers are formed in the respectivereflective regions, each of the reflective regions projects by an amountcorresponding to the thickness of the transparent resin layer, and thusthe transmissive regions are lower than that reflective regions. Namely,the substrate has an uneven surface. When a non-photosensitive colorpaste and/or a photosensitive color resist is coated on the substratehaving the uneven surface, in leveling of a color coating composition,the colored layer in each transmissive region becomes thicker than thatin each of the projecting reflective regions. In this way, leveling ofthe color coating composition can differentiate the colorcharacteristics of the reflective regions from the color characteristicsof the transmissive regions, to improve the brightness of the reflectivedisplay.

Specifically, the transparent resin layers used in the present inventionhave an average transmittance of 80% or more in the visible region. Inconsideration of a difference between the light sources, the thicknessof the transparent resin layer formed in each of the reflective regionsis selected to obtain desired characteristics such as the color purity,brightness, and color tones of the reflective regions and thetransmissive regions. In leveling of the color coating composition, thedifference in thickness between the colored layers formed in eachreflective region and each transmissive region increases as thethickness of the transparent resin increases, and thus the effect ofimproving the brightness of the reflective regions increases. When thethickness of the transparent resin layers is excessively increased, (1)the surface unevenness of the color filter increases to adversely affectthe liquid crystal alignment and thus deteriorate the display quality,and (2) the thickness of the colored layer in each reflective regioncannot be easily controlled to increase color variations. Therefore, thethickness of the transparent resin layers is preferably 5 μm or less.

Although the color of the picture elements in each of which thetransparent resin layer is formed is not particularly limited, and thetransparent resin layers may be formed in the picture elements of anyone of red, green and blue. In consideration of the characteristicdifference between the backlight used and environmental light, the coloris preferably determined to achieve the target color characteristics andbrightness. The transparent resin layer is preferably formed in eachgreen picture element to improve the color characteristics of thereflective regions because the bright of the reflective display can beimproved. The transparent resin layer is more preferably formed in eachblue picture element to improve the color characteristics of thereflective regions because the white balance of the reflective displaycan be improved.

In the color filter used in the present invention, the above-describedtwo methods may be combined in each picture element. Namely, the colorfilter may contain picture elements of at least one color in each ofwhich the transparent resin layer is disposed between the substrate andthe colored layer in the reflective region, the colored layers formed inthe reflective region and the transmissive region have differentthicknesses, and the aperture region is formed in the colored layer inthe reflective region.

Also, a plurality of colored layers may be laminated in the transmissiveregion of each of the picture elements of at least one color. Thisstructure can decrease a chromaticity difference between thetransmissive display and the reflective display. Also, the transmittancecan be improved, as compared with a color filter having aperture regionsformed in all picture elements. The color of the picture elements ineach of which the colored layers are laminated is not particularlylimited, and the colored layer may be laminated in each of the pictureelements of any one of red, green and blue. However, in consideration ofthe characteristic difference between the backlight source andenvironmental light, the color the picture elements in each of which thecolored layers are laminated is preferably determined so as to decreasethe chromaticity difference between the reflective display and thetransmissive display. Also, the area of the colored layers which arelaminated in each transmissive region is preferably determined so as todecrease the chromaticity difference between the reflective display andthe transmissive display. The coloring agents are preferably laminatedin each of the transmissive regions so as to prevent the occurrence ofspace between the boundaries and an overlap of colors. Specifically, apreferable method comprises first coating a coloring agent only in thetransmissive regions and then coating the same coloring agent in thetransmissive regions and the reflective regions, or comprises firstcoating the same coloring agent in the transmissive regions and thereflective regions and then coating another coloring agent only in thetransmissive regions.

With respect to the chromaticity difference δ between the chromaticity(x0, y0) of the transmissive regions and the chromaticity (x, y) of thereflective regions, the color filter preferably does not contain apicture element having the relation δ=(x−x0)²+(y−y0)²≧1×10⁻³, morepreferably the relation δ=(x−x0)²+(y−y0)²≧5×10⁻⁴.

The chromaticity of the transmissive regions can be determined from aspectrum in microspectrophotometer measurement of the transmissiveregions of the color filter. When each of the transmissive regions isdivided into a plurality of planar parts by laminating a plurality ofcoloring agents, the spectrum of each part is measured, and areaweighted average chromaticity is calculated. The chromaticity of thereflective regions is determined by squaring each of the spectra of thecolored region and the transparent region in a reflective region at eachwavelength, and calculating an area weighted average for the coloredregion and transparent region. Since the chromaticity is calculated withconsideration of a difference between the light sources, the calculationis preferably performed by using any one of standard light source C, atwo-peak type light source and a three-peak type light source for thetransmissive regions, and light source D65 for the reflective regions.An example of the two-peak type LED light source is a LED light sourceusing a combination of a blue LED and a yellow phosphor or ayellow-green phosphor for emitting white light. Examples of thethree-peak type light source include a three-peak fluorescent lamp, awhite LED light source comprising a combination of an ultraviolet LEDand red, blue and green phosphors, a white LED light source comprising acombination of red, blue and green LEDs, an organic electroluminescencelight source, and the like.

In the present invention, the transparent resin layers can be formed byusing a photosensitive resist. As a photosensitive resin material, amaterial such as a polyimide resin, an epoxy resin, an acryl resin, anurethane resin, a polyester resin, a polyolefin resin, or the like canbe used, and an acryl resin is preferably used. A photosensitive acrylresist generally has a composition containing at least an acryl polymer,acryl functional monomer or oligomer, and a photopolymerizationinitiator. Also, an acryl epoxy resist containing an epoxy monomer maybe used. When the transparent resin layers are formed by using thephotosensitive resist, in an exposure step of photolithographyprocessing, the surface roundness and flatness of the transparent resinlayers can be controlled by changing the distance between an exposuremask and the substrate on which the transparent resin layers are formed.

In the present invention, the transparent resin layers can also beformed by using non-photosensitive paste. As a non-photosensitive resinmaterial, a material such as a polyimide resin, an epoxy resin, an acrylresin, an urethane resin, a polyester resin, a polyolefin resin, or thelike can be used, and a polyimide resin is preferably used. When thetransparent resin layers are formed by using non-photosensitive paste,the top surfaces of the transparent resin layers can be flattened, andthe small-area transparent resin layers can be formed.

The transparent resin layers formed in the respective reflective regionsmay contain light scattering particles. When the transparent resinlayers contain the light scattering particles, dazzle in a display dueto a regular reflection component can be suppressed to achieve a goodreflective display. Since the transparent resin layers are not formed inthe transmissive regions, no light scattering occurs to permit theefficient use of the backlight. Examples of the light scatteringparticles include particles of inorganic oxides such as silica, alumina,titania, and the like, metal particles, particles of resins such as anacryl resin, a styrene resin, silicone, a fluorine-containing polymer,and the like. The light scattering particles having a particle diameterof 0.1 μm to 10 μm can be used. The light scattering particles morepreferably have a particle diameter smaller than the thickness of thetransparent resin layers because the transparent resin layers becomeflat.

In some cases, the formation of the transparent resin layersdeteriorates the surface roughness to produce step differences betweenthe surfaces of the transmissive regions and the reflective regions.Therefore, the over coat layer is preferably formed as a planarizinglayer on the picture elements. Examples of the over coat layer includean epoxy layer, an acryl epoxy layer, an acryl layer, a siloxane polymerlayer, a polyimide layer, a silicon-containing polyimide layer, apolyimidosiloxane layer, and the like.

The substrate on which the color filter is formed is not limited to thetransparent substrate such as a glass or polymer film substrate, or thelike, and the color filter may be formed on a driver element-sidesubstrate. The pattern of the color filter is not particularly limited,and a stripe shape, an island shape, or the like may be used. Also, afixed columnar spacer may be disposed on the color filter according todemand.

The picture elements are formed by a photolithography method, a printingmethod, an electrodeposition method, or the like, and the forming methodis not particularly limited. In consideration of pattern formability,the photolithography method is preferably used.

Each of the color paste and color resist used in the present inventioncontains a coloring component and a resin component. As the resincomponent, a polyimide resin, an epoxy resin, an acryl resin, a urethaneresin, a polyester resin, a polyolefin resin, or the like is preferablyused.

The photosensitive color resist contains a coloring component and aresin component containing a photosensitive component sensitive tolight. The type of the photosensitive color resist may be a positivetype in which an irradiated resin portion becomes soluble in adeveloper, or a negative type in which an irradiated resin portionbecomes insoluble in the developer. A negative resin is preferably usedbecause the photosensitive component has high transparency in thevisible region. As the resin component of the photosensitive colorresist, a polyimide resin, an epoxy resin, an acryl resin, an urethaneresin, a polyester resin, a polyolefin resin, or the like is preferablyused.

The color filter of the present invention comprises the picture elementsof at least the three colors including red, green and blue. As thecoloring agents, any of general coloring agents such as an organicpigment, an inorganic pigment, a dye, and the like may be used.Furthermore, various additives such as an ultraviolet absorber, adispersant, and the like may be added. As the dispersant, any one of awide range of agents such as a surfactant, a pigment intermediate, a dyeintermediate, a polymer dispersant, and the like may be used.Furthermore, various additives may be further added for improving acoating property and a leveling property.

Examples of a pigment include Pigment Red (PR-) 2, 3, 9, 22, 38, 81, 97,122, 123, 144, 146, 149, 166, 168, 169, 177, 179, 180, 190, 192, 206,207, 209, 215, 216, 224, 242, 254, and 266; Pigment Green (PG-) 7, 10,36, 37, 38, and 47; Pigment Blue (PB-) 15 (15:1, 15:2, 15:3, 15:4,15:6), 16, 17, 21, 22, 60, and 64; Pigment Yellow (PY-) 12, 13, 14, 17,20, 24, 83, 86, 93, 94, 95, 109, 110, 117, 125, 129, 137, 138, 139, 147,148, 150, 153, 154, 155, 166, 173, 180, and 185; Pigment Violet (PV-)19, 23, 29, 30, 32, 33, 36, 37, 38, 40, and 50; Pigment Orange (PO-) 5,13, 17, 31, 36, 38, 40, 42, 43, 51, 55, 59, 61, 64, 65, and 71. Thesepigments may be used singly or in a combination of at least twopigments.

The pigment may be surface-treated by rosin treatment, acidifiedtreatment, basified treatment, pigment derivative treatment or the likeaccording to demand.

PR (Pigment Red), PY (Pigment Yellow), PV (Pigment Violent; and PO(Pigment Orange) are symbols in the color index (C. I.: issued by TheSociety of Dyers and Colourists), and C. I. is officially added at thetop (for example, C. I. PR254). These symbols define the standards ofdyes and dyeing, and each of the symbols defines a specified standarddye and its color. In the description below, as a rule, C. I. is omitted(for example, C. I. PR254 is shown as PR254).

As a method for coating the non-photosensitive color paste orphotosensitive color resist, a dipping method, a roll coater method, aspin coating method, a die coating method, a combined method comprisingdie coating and spin coating, a wire bar coating method, or the like ispreferably used.

An example of the method for forming the transparent resin layers byusing the non-photosensitive paste will be described below. First, thenon-photosensitive paste is coated on the transparent substrate and thendried (semicured) by hot plate heating, oven heating, or vacuum drying.Then, a positive photoresist is coated on the semicured layer, and thendried (pre-baked) by heating. After pre-baking, mask exposure and alkalidevelopment are performed to dissolve the photoresist in a solvent,forming the transparent resin layers which are then cured by heating.

An example of the method for forming the transparent resin layers byusing the photosensitive resin will be described below. First, thephotosensitive paste is coated on the transparent substrate and thendried (pre-baked) by hot plate heating, oven heating, or vacuum drying.After pre-baking, mask exposure, alkali development and heat curing areperformed to obtain the transparent resin layers.

An example of the method for forming the colored picture elements willbe described below. First, for example, the non-photosensitive colorpaste is coated on the transparent substrate or the transparentsubstrate having the transparent resin layers formed in the reflectiveregions of the picture elements, and then heat-dried (semicured) by ahot plate, an oven, or vacuum drying. Then, a positive photosensitiveresist is coated on the semicured layer and heat-dried (pre-baked).After pre-baking, mask exposure, alkali development and heat curing areperformed.

The present invention is described above with reference to the examplein which the colored layers are formed to different thicknesses byforming the transparent resin layers in the reflective regions and byleveling the color coating composition. However, another method may beused. For example, the curing thickness of each colored layer comprisinga photosensitive color resist can be changed by changing an exposureamount in mask exposure in a photolithography process. Although the useof an acryl resin as the resin component is described, thephotosensitive color resist of the present invention is not limited tothis. In photolithography of the photosensitive color resist, with asufficient amount of exposure, photocrosslinkage of the photosensitivecolor resist proceeds, and thus an exposed portion becomes insoluble inthe developer. An unexposed portion is soluble in the developer becausephotocrosslinkage of the acryl resin does not proceed. On the otherhand, with an exposure insufficient for curing the photosensitive resin,photocrosslinkage of the acryl resin does not sufficiently proceed, andthus an exposed portion is partially soluble in the developer.Therefore, the thickness of the photosensitive resin can be controlledby controlling the exposure.

As a method for controlling the exposure, a method using asemi-transparent photomask, or a method using a photomask having slitsor dots may be used. The semi-transparent photomask has asemi-transparent region having a transmittance of 0 and more and lessthan 100%. By using the semi-transmitting photomask, the thickness canbe controlled by using a large-exposure portion and a small-exposureportion. A slit photomask has a slit having a width of 20 μm or less andformed in a light shielding portion of the photomask so that an averagequantity of light transmitted through the slits per unit area iscalculated to control the exposure. A dot photomask has at least onecircular, elliptic, square, rectangular, rhombic, or trapezoidal dothaving an area of 400 μm² or less and formed in a light shieldingportion so that an average quantity of light transmitted through slitsper unit area is averaged to control the exposure.

The transflective liquid crystal display of the present inventioncomprises a combination of the color filter having the picture elementsof at least the tree colors including red, green and blue, and thethree-peak type backlight source.

In the present invention, it is important that the backlight source isthe three-peak type light source, and that a side peak due to animpurity component other than the three peaks corresponding to the red,green and blue colors is absent or small to produce a sharp spectralshape. Any of general light sources such as a cold cathode fluorescentlamp, a hot cathode fluorescent lamp, a light emitting diode (LED), anorganic electroluminescence light source, an inorganicelectroluminescence light source, a planar fluorescent lamp, a metalhalide lamp, and the like may be used as long as the light sourcesatisfies the above condition. However, it was found that the three-peaktype LED light source has a significant effect on the object of thepresent invention to achieve the high color reproducibility of thetransmissive display and the excellent characteristics (colorreproducibility and brightness) of the reflective display.

As the three-peak type LED light source, a white light source comprisinga combination of RGB light emitting diodes, or a white light sourcecomprising a combination of an ultraviolet light emitting diode and RGBphosphors may be used. For example, a chip LED “GM1WA80350A” produced bySharp Corporation may be used. An example of the white LED light sourcecomprising a combination of an ultraviolet light emitting diode and RGBphosphors is a white LED produced by Toyoda Gosei Co., Ltd. (NikkeiElectronics, 2002, Vol. 2-25).

In consideration of a difference between the light sources, colorcharacteristics of the picture elements are preferably designed by usingthe backlight source for the transmissive regions and the light sourceD65 close to sunlight (natural light) for the reflective regions.

In the transflective liquid crystal display of the present invention, adriving system and display system are not limited. An active matrixsystem, a passive matrix system, a TN mode, a STN mode, an ECB mode, anOCB mode, and the like may be used for the liquid crystal display. Also,the configuration of the liquid crystal display, for example, the numberof polarization plates, the position of a scatterer, and the like, isnot particularly limited.

An example of the method for manufacturing the color filter used in thepresent invention will be described.

A color paste comprising at least a polyimide precursor (polyamic acid),a coloring agent, and a solvent is coated on the transparent substrateand then dried by air drying, heat drying or vacuum drying to form apolyamic acid colored film. Heat drying is preferably performed by usingan oven or a hot plate in the range of 50° C. to 180° C. for 1 minute to3 hours. Then, the polyamic acid colored film obtained as describedabove is patterned by usual wet etching. First, a positive photoresistis coated on the polyamic acid colored film to form a photoresist film.Then, a mask having a picture element pattern of each color or a maskhaving a pattern for forming apertures as occasion demands is placed onthe photoresist film, and then irradiated with ultraviolet light usingan exposure apparatus. After exposure, the photoresist film and thepolyamic acid colored film are simultaneously etched with an alkalideveloper for positive photoresist. After etching, the unnecessaryphotoresist film is removed.

Then, the polyamic acid colored layer is heat-treated to be converted toa polyimide colored film. The heat treatment is performed continuouslyor stepwisely in air, a nitrogen atmosphere or vacuum at 150° C. to 350°C., preferably 180′ C. to 250′ C., for 0.5 to 5 hours.

When the color filter substrate having the transparent resin layersformed in the respective reflective regions is formed, anon-photosensitive paste comprising polyamic acid and a solvent iscoated over the entire surface of the transparent substrate, and thenheat-dried by using a hot plate in the range of 60° C. to 200′ C. for 1minute to 60 minutes. Next, a positive photoresist is coated on thepolyamic acid film obtained as described above, and then heat-dried byusing a hot plate in the range of 60° C. to 150° C. for 1 minute to 30minutes. Then, the intended pattern is baked by ultraviolet irradiationusing an exposure apparatus, followed by an alkali development to obtainthe transparent resin layers in a desired pattern at a desired position.The resultant transparent resin layers are heat-cured at 200° C. to 300°C. Next, the colored layers are formed in each of the picture elementsin each of which the transparent resin layer is formed in the reflectiveregion, the colored layers in the transmissive and reflective regions ineach picture element having different thicknesses due to the transparentresin layer formed in the reflective region. A photosensitive colorresist comprising a photosensitive acryl resin comprising at least anacryl polymer, an acryl polyfunctional monomer, and aphotopolymerization initiator, a coloring agent and a solvent is coatedand then dried by air drying, heat drying or vacuum drying to form aphotosensitive acryl colored film. The heat drying is preferablyperformed by using an oven, a hot plate, or the like in the range of 60°C. to 200° C. for 1 minute to 3 hours. Then, the photosensitive acrylcolored film is irradiated in the form of a pattern with ultravioletrays using an exposure apparatus through a photomask. After exposure,the photosensitive acryl colored film is etched with an alkalideveloper.

The above-described process is performed for the picture elements ofeach of red, green and blue (a black matrix as occasion demands), and ifrequired, the over coat layer for planarization and a transparentconductive film of ITO or the like are deposited to form the colorfilter for the liquid crystal display.

Next, an example of the transflective liquid crystal display using thecolor filter will be described. First, a transparent protective film isformed on the color filter, and a transparent electrode comprising anITO film or the like is formed on the protective film. Next, the colorfilter substrate is opposed to a transflective substrate on which atransflective film having a metallized film pattern, a transparentinsulating film formed on the transfective film, and a transparentelectrode comprising an ITO film or the like are formed. Also, a liquidcrystal alignment film provided on each of the substrates and subjectedto rubbing for liquid crystal alignment, and a spacer for maintainingthe cell gap are interposed between both substrates opposed to eachother and sealed together. Besides the reflection layer and thetransparent electrode, light diffusion projections, thin-film transistor(TFT) devices or thin-film diode (TFD) devices, scanning lines andsignal lines are provided on the transflective substrate to form a TFTliquid crystal display or TFD liquid crystal display. Next, a liquidcrystal is injected through an injection hole provided at the sealedportion, and then the injection port is sealed. Next, a driver IC andthe like are mounted to complete a module.

Next, an example of the method for forming the backlight source used inthe present invention will be described.

For the backlight source using a LED, LED devices are arranged on asubstrate on which wiring is patterned for applying a necessary voltage,a driver IC is mounted on the substrate, and then a diffusion plate, alight guide plate, a prism sheet, a guide rod, and the like areappropriately combined to complete the backlight source.

For a three-peak type fluorescent lamp, a fluorescent slurry comprisingan inorganic phosphor corresponding to each of the red, green and bluecolors, an organic solvent such as butyl acetate, and a binder resinsuch as nitrocellulose is coated on the inner wall of a cylindricalglass tube by vacuum suction, and then heat-treated at a temperature of400° C. to 650° C. for 3 minutes to 20 minutes to bake the phosphor andremove gases. Next, the glass tube is evacuated to a vacuum of 10⁻² to10⁻⁵ Torr, and an argon gas or a mixture of argon gas and neon gas,krypton gas, xenon gas, or the like is sealed in the glass tube. Amercury dispenser previously provided on an electrode portion is heatedwith a radio frequency wave to diffuse mercury in the tube. Finally,aging is performed for several hours to complete the three-peak typefluorescent lamp. The thus-obtained three-peak fluorescent lamp, adiffusion plate, a light guide, a prism sheet, a guide rod, and the likeare appropriately combined to complete the backlight source.

For the backlight source using organic electroluminescence, first apositive photoresist is coated to a desired thickness on an ITO glasssubstrate by spin coating. The resultant coated film is patterned byexposure through a mask, subjected to development to form a pattern, andthen cured. Next, a thin-film layer pattern containing a hole transportlayer and an emitting layer is formed by vacuum deposition, and then anelectron transport layer and aluminum are deposited to a predeterminedthickness. The substrate is bonded to a sealing plate with a curableepoxy resin and sealed therewith to complete the organicelectroluminescence light source.

EXAMPLES

<Measurement Method>

Transmittance and color coordinates: A glass substrate having an ITOfilm deposited thereon under the same deposition conditions as thoseused for a color filter was measured as a reference by using OTSUKAELECTRONICS Co., Ltd., Multi Channel Photo Detector “MCPD-2000”.

The transmissive region chromaticity can be determined from a spectrumobtained in measurement of the transmissive regions of the color filterusing a microspectrophotometer or the like. When each of thetransmissive regions is divided into a plurality of planar parts bylaminating a plurality of coloring agents, the spectrum of each part ismeasured, and area weighted average chromaticity is calculated. Thereflective region chromaticity is determined by squaring each of thespectra of the colored region and transparent region in a reflectiveregion at each wavelength, and calculating an area weighted average forthe colored region and transparent region.

Although the present invention will be described in detail below withreference to examples, the present invention is not limited to theseexamples.

In each of the examples and comparative examples below, the ratio of areflection plate (reflective region) to the aperture of each pictureelement was 50% unless otherwise specified. Also, a transparent resinlayer was formed in the reflective region of each picture element.

Example 1

A. Formation of Polyamic Acid Solution

95.1 g of 4,4′-diaminodiphenyl ether and 6.2 g ofbis(3-aminopropyl)tetramethyl disiloxane were charged together with 525g of γ-butyrolactone and 220 g of N-methyl-2-pyrrolidone, and 144.1 g of3,3′,4,4′-biphenyltetracarboxylic acid dianhydride was added to theresultant mixture. After reaction at 70° C. for 3 hours, 3.0 g ofphthalic anhydride was added to the reaction solution, followed byfurther reaction at 70° C. for 2 hours to obtain a 25 wt % solution ofpolyamic acid (PAA).

B. Synthesis of Polymer Dispersant

161.3 g of 4,4′-diaminobenzanilide, 176.7 g of 3,3′-diaminodiphenylsulfone and 18.6 g of bis(3-aminopropyl)tetramethyl disiloxane werecharged together with 2667 g of γ-butyrolactone and 527 g ofN-methyl-2-pyrrolidone, and 439.1 g of 3,3′,4,4′-biphenyltetracarboxylicacid dianhydride was added to the resultant mixture. After reaction at70° C. for 3 hours, 2.2 g of phthalic anhydride was added to thereaction solution, followed by further reaction at 70° C. for 2 hours toobtain a 20 wt % solution of polyamic acid (PAA) as a polymer dispersant(PD).

C. Formation of Non-photosensitive Color Paste

4.5 g of, Pigment Red PR254, 22.5 g of the polymer dispersant (PD), 42.8g of γ-butyrolactone and 20.2 g of 3-methoxy-3-methyl-1-butanol werecharged together with 90 g of glass beads, and the resultant mixture wasdispersed by a homogenizer for 5 hours at 7000 rpm. Then, the glassbeads were filtered off to obtain a 5% dispersion solution (RD)comprising PR254.

Then, a solution obtained by diluting 8.0 g of the polyamic acidsolution (PAA) with 50.0 g of γ-butyrolactone was added and mixed with25.5 g of the dispersion solution (RD) to obtain red color paste(RPI-1). Similarly, each of red paste (R-1, R-2, R-3, R-4, R-5, andR-6), green paste (GPI-1, G-1, G-2, G-3, G-4, and G-5) and blue paste(BPI-1, B-1, B-2, B-3, B-4, and B-5) shown in Table 1 was obtained.

D. Formation of Non-photosensitive Paste (Used for Transparent ResinLayers)

16.0 g of the polyamic acid solution (PAA) was diluted with 34.0 g ofγ-butyrolactone to obtain non-photosensitive transparent paste (TPI-1).

E. Formation of Photosensitive Color Resist

35.2 g of Pigment Red PR254 was charged together with 200 g of3-methyl-3-methoxybutanol, and the resultant mixture was dispersed by ahomogenizer at 7000 rpm for 5 hours. The glass beads were filtered offto obtain a dispersion solution. On the other hand, 130.00 g ofcyclopentanone was added to 35.00 g of an acryl copolymer solution(DAICEL Chemical Industries, LTD. “SAIKUROMA P, ACA-250”, 43 wt %solution), 15.00 g of pentaerythritol tetramethyl acrylate as apolyfunctional monomer, and 7.50 g of “IRGACURE 369” as aphotopolymerization initiator to obtain a 20 wt % solution ofphotosensitive acryl resin (AC-1). Then, 20 g of the red dispersionsolution was added to 38.5 g of the photosensitive acryl resin solution(AC-1) to form a red resist (RAC-1). Similarly, a red resist (RAC-2),green resists (GAC-1 and GAC-2), blue resists (BAC-1 and BAC-2) shown inTable 1 were obtained.

TABLE 1 Pigment/Resin (ratio by Paste No. Pigment Composition (wt %)weight) RPI-1 PR254 = 100 28/72 GPI-1 PG36/PY138 = 55/45 42/58 BPI-1PB15:6/PV23 = 96/4 35/65 RAC-1 PR254 = 100 28/72 GAC-1 PG36/PY138 =55/45 42/58 BAC-1 PB15:6/PV23 = 96/4 35/65 R-1 PR209/PO38 = 85/15 33/67R-2 PR209/PO38 = 70/30 25/75 R-3 PR209/PO38 = 30/70 17/83 R-4PR254/PR122 = 85/15 11/89 R-5 PR254 = 100 23/77 R-6 PR254/PR138 = 85/1514/86 G-1 PG36/PY138 = 75/25 17/83 G-2 PG36 = 100 32/68 G-3 PG36/PY138 =85/25 26/74 G-4 PG36/PY138 = 70/30 40/60 G-5 PG36/PY138 = 55/45 15/85B-1 PB15:6 = 100 17/83 B-2 PB15:6/PV23 = 93/7 12/88 B-3 PB15:6 = 100 8/92 B-4 PB15:6 = 100 25/75 B-5 PB15:6/PV23 = 96/4 12/88

F. Formation and Evaluation of Colored Film

The red paste (RPI-1) was coated by a spinner on a glass substratehaving a black matrix pattern formed thereon. The coating film was driedat 120° C. for 20 minutes, and then a positive photoresist (TOKYO OHKAKOUGYO CO., LTD. “OFPR-800”) was coated on the resultant film and driedat 90° C. for 10 minutes. The resultant coating film was exposed tolight by using Canon Inc. “Proximity Exposure “PLA-501F” through achromium photomask with a strength of 60 mJ/cm² (strength of ultravioletlight at 365 nm). The photomask used had an aperture ratio (apertureregion ratio) of 11% in the reflective regions. After exposure, thesubstrate was dipped in a developer comprising a 2.0% aqueous solutionof tetramethylammonium hydroxide to simultaneously perform developmentof the photoresist and-etching of the colored film of polyimideprecursor. After etching, the unnecessary photoresist layer was removedwith acetone. Furthermore, the colored film of a polyamide precursor washeat-treated at 240° C. for 30 minutes to convert the polyamideprecursor to polyimide. The coating thickness in each of a transmissiveregion and a reflective region after heat treatment was 1.2 μm, and thechromaticity (x, y) of the transmissive regions, which was measured byusing standard light source C, was (0.567, 0.310).

Next, the color paste (GPI-1) was coated by a spinner, and thenphotolithography was performed by the same method as that used for thered picture elements except that a photomask having an aperture ratio of27% in a reflective region, to form colored layers. The thickness of thegreen colored layer in each of the transmissive regions and thereflective regions was 1.2 μm, and the chromaticity (x, y) of thetransmissive regions, which was measured by using standard light sourceC, was (0.321, 0.541).

Next, the color paste (BPI-1) was coated by a spinner, and thenphotolithography was performed by the same method as that used for thered picture elements except that a photomask having an aperture ratio of13% in a reflective region, to form colored layers. The thickness of theblue colored layer in each of the transmissive regions and thereflective regions was 1.2 μm, and the final chromaticity (x, y) of thetransmissive regions, which was measured by using standard light sourceC, was (0.138, 0.127). Then, an over coat layer (JSR Corporation,“Optomer SS6500/SS0500”) was deposited to a thickness of 2 μm on thepicture element layer. Then, an ITO film was deposited to a thickness of0.1 μm by sputtering on the over coat layer. For the thus-obtained colorfilter substrate, the spectrum of each of the central picture elementand the four corner picture elements of the substrate was measured. Thespectra measured at the respective measurement portions were averaged.FIG. 10 shows the resulting spectrum (transmissive region spectrum), andFIG. 11 shows the spectrum (reflective region spectrum of anarea-controlling system color filter) obtained from an area weightedaverage of the spectra of the colored region and the transparent regionof a reflective region.

G. Formation of Backlight Source

A two-peak type white LED “NSSW440” produced by NICHIA Corporation wasdisposed on a substrate having a wiring pattern, and driver IC wasmounted on the substrate. Then, a reflection plate, a light guide, adiffusion plate, and a prism sheet were combined to the substrate toform a backlight source. Similarly, a backlight source was formed byusing each of a three-peak type white LED (ultraviolet LED+RGBphosphors), and a three-peak type white LED (RGB three chip LEDs).

Each of Y₂O₃:Eu, LaPO₄:Tb, Ce and BaMg₂Al₁₆O₂₇:Eu used as the red, greenand blue phosphors, respectively, was mixed with butyl acetate andnitrocellulose to prepare a fluorescent slurry. Then, the fluorescentslurry was coated on the inner surface of a cylindrical glass tubehaving a diameter of 2 mm, and heat-treated at 550° C. for 5 minutes tobake the phosphor. The glass tube was evacuated to a vacuum of 10⁻⁴Torr, and then a mixed gas containing argon gas and xenon gas was sealedin the tube. Then, mercury was diffused in the tube to form a three-peaktype fluorescent lamp. The thus-formed three-peak type fluorescent lampwas combined with a reflection plate, a light guide, a diffusion plate,and a prism sheet to form a backlight source.

Furthermore, an organic electroluminescence light source was formed asfollows. A positive photoresist (TOKYO OHKA KOUGYO CO., LTD. “OFPR-800”)was coated to a thickness of 3 μm on an ITO glass substrate (GEOMATECCo., Ltd.) by a spin coating method. The resultant coating film wasexposed to light in the form of a pattern-through a photomask, and thensubjected to development to form a photoresist pattern. After thedevelopment, the pattern was cured at 160° C. Next, a thin-film layerincluding an emitting layer was formed by a vacuum deposition method ina resistance wire heating system through a shadow mask. In vacuumdeposition, the degree of vacuum was 2×10⁻⁴ Pa, and the substrate wasrotated with respect to a deposition source. First, 15 nm of copperphthalocyanine and 60 nm ofN,N′-diphenyl-N,N′-bis(1-naphthyl)-1,1′-diphenyl-4,4′-diamine (α-NPD)were deposited over the entire surface of the substrate to form a holetransport layer. Next, tris(8-quinolinolato) aluminum (III) (Alq3)serving as a host material,2,3,5,6-1H,4H-tetrahydro-9-(2′-benzothiazolyl)quinolizino [9,9a,1-gh]cumarin (C545) serving as a dopant material were co-deposited sothat the dopant content was 1.0% by weight to form a green lightemitting layer pattern. Next, the shadow mask was shifted by a lengthcorresponding to one pitch, and Alq3 as a host material and4-(dicyanomethylene)-2-methyl-6-(1,1,7,7-tetramethyldurolysyl-9-enyl)-4H-pyrane(DCJT) serving as a guest material were co-deposited so that the dopantcontent was 2.0% by weight to form a red light emitting layer pattern.Furthermore, the shadow mask was shifted by a length corresponding toone pitch, and 4,4′-bis(2,2′-diphenylvinyl)diphenyl (DPVBi) wasdeposited to a thickness of 20 nm to form a blue light emitting layerpattern. Next, 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline wasdeposited to a thickness of 45 nm over the entire surface of thesubstrate to form an electron transport layer. Then, the thin-film layerwas exposed to lithium vapor for doping (0.5 nm in terms of thickness).Next, aluminum used for a counter electrode was deposited to a thicknessof 400 nm. The substrate on which the counter electrodes was formed wasremoved from the deposition apparatus, maintained for 20 minutes under areduced-pressure atmosphere created by a rotary pump, and thentransferred to an argon atmosphere at a dew point −100° C. or less. Inthe low-humidity atmosphere, the substrate and a sealing plate werebonded together with a curing epoxy resin.

FIGS. 1 to 5 respectively show the spectra of the three-peak type lightsources and the two-peak type LED formed as described above.

Example 2

A color filter substrate was formed by the same method as in Example 1except that photomasks having aperture region ratios of 14%, 43% and 18%were used for photolithography of red, green and blue picture elements,respectively. Then, an over coat layer and an ITO film were deposited onthe resultant picture element film by the same method as in Example 1.For the thus-formed color filter substrate, the spectrum of each of thecentral picture element and the four corner picture elements of thesubstrate was measured. The measured spectra of the picture elementswere averaged.

Comparative Example 1

A color filter-substrate was formed by the same method as in Example 1except that a colored film of each of red, green and blue pictureelements was deposited to a thickness of 1.8 μm, and photomasks havingaperture region ratios of 14%, 40% and 17% were for photolithography ofred, green and blue picture elements, respectively. As a result ofmeasurement of the chromaticity of the transmissive region of each ofthe red, green, and blue picture elements by using standard light sourceC, the degrees of chromaticity (x, y) of the red, green, and bluepicture elements were (0.622, 0.328), (0.298, 0.581), and (0.135,0.099), respectively. Then, an over coat layer and an ITO film weredeposited on the resultant picture element film by the same method as inExample 1. For the thus-formed color filter substrate, the spectrum ofeach of the central picture element and the four corner picture elementsof the substrate was measured. The measured spectra of the pictureelements were averaged. FIG. 10 shows the spectrum (transmissive regionspectrum) obtained in Comparative Example, and the spectrum obtained inExample 1.

Table 2 show the reflection region chromaticity of the colored filmsmeasured with light source D65 and the transmissive region chromaticitymeasured with a three-peak type LED light source (ultraviolet LED+RGBphosphors) in each of the Examples 1 and 2, and the reflective regionchromaticity of the colored films measured with light source D65 and thetransmissive region chromaticity measured with a two-peak type LED lightsource in Comparative Example 1.

TABLE 2 Reflective region chromaticity (light source Transmissive regionchromaticity D65) Color re- Light Color repro- Brightness(Y x y Yproducibility source x y Y ducibility*1) value of W)*1) Example R 0.6180.294 32.4 60% Three-peak R 0.519 0.332 27.5 23% (+52%) 36.9 1 G 0.2710.596 62.0 type LED G 0.302 0.454 64.3 B 0.137 0.165 20.1 (UV-LED + B0.195 0.170 18.9 W 0.336 0.341 38.2 RGB W 0.320 0.330 36.9 Example R0.618 0.294 32.4 phosphors) R 0.497 0.332 29.8 15% 41.3 (+12%) 2 G 0.2710.596 62.0 G 0.306 0.409 70.8 B 0.137 0.165 20.1 B 0.211 0.192 23.2 W0.336 0.341 38.2 W 0.320 0.323 41.3 Comp. R 0.630 0.349 23.4 60%Two-peak R 0.496 0.331 27.7 15% 36.9 Example G 0.333 0.576 57.3 type LEDG 0.299 0.409 63.2 1 B 0.132 0.090 8.6 B 0.221 0.194 19.8 W 0.336 0.34129.8 W 0.324 0.325 36.9 *1)(Improvement over Comparative Example)

In comparison between the color characteristics of a combination of thecolor filter of Example 1 and a backlight source and a combination ofthe color filter of Comparative Examples 1 and a backlight source, bothcombinations equal in the color reproducibility range with thetransmissive region chromaticity and brightness with the reflectiveregion chromaticity. However, the range of color reproducibility in thereflective regions of the color filter of Example 1 is 52% higher thanthat of Comparative Example 1. In comparison between the colorcharacteristics of a combination of the color filter of Example 2 and abacklight source and a combination of the color filter of ComparativeExample 1 and a backlight source, both combination are equal in thecolor reproducibility range with the transmissive region chromaticityand the color reproducibility range with the reflective regionchromaticity. However, brightness of the reflective regions of the colorfilter of Example 2 is 12% higher than that of Comparative Example 1.

In comparison between the display characteristics of a liquid crystaldisplay comprising the color filter of each of Examples 1 and 2 and athree-peak type LED light source (ultraviolet LED+RGB phosphors) and aliquid crystal display comprising the color filter of ComparativeExample 2 and a two-peak type LED light source, the liquid crystaldisplays are equal in the color vividness of a transmissive display.Although the liquid crystal displays of Example 1 and ComparativeExample 1 are equal in brightness of a reflective display, the liquidcrystal display of Example 1 exhibits higher color vividness and highervisibility. In comparison between the liquid crystal displays of Example2 and Comparative Example 1, both liquid crystal display are equal inthe color reproducibility range in a reflective display. However, theliquid crystal display of Example 2 exhibits higher brightness andhigher visibility even in the dark.

Example 3

A color filter substrate was formed by the same method as in Example 1except that a colored film of each of red, green and blue pictureelements was deposited to a thickness of 1.1 μm, and photomasks havingaperture region ratios of 10%, 27% and 10% were used forphotolithography of red, green and blue picture elements, respectively.As a result of measurement of the transmissive region chromaticity ofeach of the red, green and blue picture elements by using standard lightsource C, the degrees of chromaticity (x, y) of the red, green and bluepicture elements were (0.551, 0.305), (0.324, 0.531), and (0.139,0.135), respectively. Then, an over coat layer and an ITO film weredeposited on the resultant picture element film by the same method as inExample 1. For the thus-formed color filter substrate, the spectrum ofeach of the central picture element and the four corner picture elementsof the substrate was measured. The measured spectra of the pictureelements were averaged.

Example 4

A color filter substrate was formed by the same method as in Example 3except that photomasks having aperture region ratios 14%, 43% and 19%were used for photolithography of red, green and blue picture elements,respectively. Then, an over coat layer and an ITO film were deposited onthe resultant picture element film by the same method as in Example 1.For the thus-formed color filter substrate, the spectrum of each of thecentral picture element and the four corner picture elements of thesubstrate was measured. The measured spectra of the picture elementswere averaged.

Table 3 shows the reflective region chromaticity of the colored filmsmeasured with light source D65 and the transmissive region chromaticitymeasured with a three-peak type LED light source (RGB chip LEDs) in eachof Examples 3 and 4, and the reflective region chromaticity of thecolored films measured with light source D65, and the transmissiveregion chromaticity measured with a two-peak type LED light source inComparative Example 2.

TABLE 3 Transmissive region chromaticity Reflective region chromaticity(light source D65) Color re- Light Color repro- Brightness(Y x y Yproducibility source x y Y ducibility*1) value of W)*1) Example R 0.6480.287 31.5 60% Three-peak R 0.526 0.332 27.5 26% (+73%) 36.9 3 G 0.2550.574 62.3 type LED G 0.304 0.454 66.1 B 0.130 0.184 22.1 (RGB -LED) B0.181 0.157 17.2 W 0.337 0.342 38.6 W 0.319 0.328 36.9 Example R 0.6480.287 31.5 R 0.496 0.331 30.5 15% 42.5 (+15%) 4 G 0.255 0.574 62.3 G0.307 0.410 72.3 B 0.130 0.184 22.1 B 0.211 0.196 24.9 W 0.337 0.34238.6 W 0.320 0.323 42.5 Comp. R 0.630 0.349 23.4 60% Two-peak R 0.4960.331 27.7 15% 36.9 Example G 0.333 0.576 57.3 type LED G 0.299 0.40963.2 1 B 0.132 0.090 8.6 B 0.221 0.194 19.8 W 0.336 0.341 29.8 W 0.3240.325 36.9 *1)(Improvement over Comparative Example)

In comparison between the color characteristics of a combination of thecolor filter of Example 3 and a backlight source and a combination ofthe color filter of Comparative Examples 1 and a backlight source, bothcombination are equal in the color reproducibility range with thetransmissive region chromaticity and brightness with the reflectiveregion chromaticity. However, the range of color reproducibility in thereflective regions of the color filter of Examples 3 is 73% higher thanthat of Comparative Example 1. In comparison between the colorcharacteristics of a combination of the color filter of Example 4 and abacklight source and a combination of the color filter of ComparativeExample 1 and a backlight source, the combinations are equal in thecolor reproducibility range with the transmissive region chromaticityand the color reproducibility range with the reflective regionchromaticity. However, brightness of the reflective regions of the colorfilter of Example 4 was 15% higher than that of Comparative Example 1.

In comparison between the display characteristics of a liquid crystaldisplay comprising the color filter of each of Examples 3 and 4 and athree-peak type LED light source (RGB chip LEDs) and a liquid crystaldisplay comprising the color filter of Comparative Example 2 and atwo-peak type LED light source, the liquid crystal displays are equal inthe color vividness of a transmissive display. Although the liquidcrystal displays of Example 3 and Comparative Example 1 are equal in thebrightness of a reflective display, the liquid crystal display ofExample 3 exhibits higher color vividness and higher visibility. Incomparison between the liquid crystal displays of Example 4 andComparative Example 1, both liquid crystal displays are equal in thecolor reproducibility range in a reflective display. However, the liquidcrystal display of Example 4 exhibits higher brightness and highervisibility even in the dark.

Comparative Example 2

A color filter substrate was formed by the same method as in Example 1except that a colored film of each of red, green and blue pictureelements was deposited to a thickness of 1.6 μm, and photomasks havingaperture region ratios of 13%, 37% and 16% were used forphotolithography of red, green and blue picture elements, respectively.As a result of measurement of the transmissive region chromaticity ofeach of the red, green and blue picture elements by using standard lightsource C, the degrees of chromaticity (x, y) of the red, green and bluepicture elements were (0.606, 0.322), (0.311, 0.566), and (0.136,0.108), respectively. Then, an over coat layer and an ITO film weredeposited on the resultant picture element film by the same method as inExample 1. For the thus-formed color filter substrate, the spectrum ofeach of the central picture element and the four corner picture elementsof the substrate was measured. The measured spectra of the pictureelements were averaged.

Comparative Example 3

A color filter substrate was formed by the same method as in ComparativeExample 2 except that photomasks having aperture region ratios of 14%,41% and 17% were used for photolithography of red, green and bluepicture elements, respectively. Then, an over coat layer and an ITO filmwere deposited on the resultant picture element film by the same methodas in Example 1. For the thus-formed color filter substrate, thespectrum of each of the central picture element and the four cornerpicture elements of the substrate was measured. The measured spectra ofthe picture elements were averaged.

Comparative Example 4

A color filter substrate was formed by the same method as in Example 1except that a colored film of each of red, green and blue pictureelements was deposited to a thickness of 1.5 μm, and photomasks havingaperture region ratios of 13%, 35% and 15% were used forphotolithography of red, green and blue picture elements, respectively.As a result of measurement of the transmissive region chromaticity ofeach of the red, green and blue picture elements by using standard lightsource C, the degrees of chromaticity (x, y) of the red, green and bluepicture elements were (0.599, 0.320), (0.313, 0.561), and (0.136,0.111), respectively. Then, an over coat layer and an ITO film weredeposited on the resultant picture element film by the same method as inExample 1. For the thus-formed color filter substrate, the spectrum ofeach of the central picture element and the four corner picture elementsof the substrate was measured. The measured spectra of the pictureelements were averaged.

Comparative Example 5

A color filter substrate was formed by the same method as in ComparativeExample 3 except that photomasks having aperture region ratios of 14%,41% and 18% were used for photolithography of red, green and bluepicture elements, respectively. Then, an over coat layer and an ITO filmwere deposited on the resultant picture element film by the same methodas in Example 1. For the thus-formed color filter substrate, thespectrum of each of the central picture element and the four cornerpicture elements of the substrate was measured. The measured spectra ofthe picture elements were averaged.

Table 4 shows the reflective region chromaticity of the colored filmsmeasured with light source D65 and the transmissive region chromaticitymeasured with a three-peak type LED light source in each of ComparativeExamples 2 and 3, the reflective region chromaticity of the coloredfilms measured with light source D65 and the transmissive regionchromaticity measured with an organic electroluminescence (EL) lightsource in each of Comparative Examples 4 and 5, and the reflectiveregion chromaticity of the colored film measured with light source D65and the transmissive region chromaticity measured with a two-peak typeLED light source in Comparative Example 1.

TABLE 4 Transmissive region chromaticity Reflective region chromaticity(light source D65) Color re- Light Color repro- Brightness(Y x y Yproducibllity source x y Y ducibility*1) value of W)*1) Comp. R 0.6300.349 23.4 60% Two-peak R 0.496 0.331 27.7 15% 36.9 Example G 0.3330.576 57.3 type LED G 0.299 0.409 63.2 1 B 0.132 0.090 8.6 B 0.221 0.19419.8 W 0.336 0.341 29.8 W 0.324 0.325 36.9 Comp. R 0.608 0.329 24.2 60%Three-peak R 0.501 0.332 27.2 17% (+13%) 36.9 Example G 0.324 0.587 64.9type G 0.301 0.419 64.0 2 B 0.146 0.080 7.8 fluorescent B 0.212 0.18619.7 W 0.336 0.345 32.3 light source W 0.322 0.326 36.9 Comp. R 0.6080.329 24.2 60% Three-peak R 0.494 0.332 27.9 15% 38.1 (+3%) Example G0.324 0.587 64.9 type G 0.303 0.409 66.0 3 B 0.146 0.080 7.8 fluorescentB 0.216 0.190 20.5 W 0.336 0.345 32.3 light source W 0.321 0.324 38.1Comp. R 0.638 0.321 28.5 60% Three-peak R 0.502 0.332 27.5 18% (+20%)36.9 Example G 0.289 0.565 59.7 type G 0.301 0.426 64.0 4 B 0.129 0.13514.2 organic EL B 0.207 0.180 19.1 W 0.336 0.341 34.1 light source W0.321 0.326 36.9 Comp. R 0.638 0.321 28.5 60% Three-peak R 0.494 0.33228.3 15% 38.9 (+5%) Example G 0.289 0.565 59.7 type G 0.303 0.410 66.8 5B 0.129 0.135 14.2 organic EL B 0.217 0.194 21.7 W 0.336 0.341 34.1light source W 0.321 0.324 38.9 *1)(Improvement over ComparativeExample)

In comparison between the color characteristics of a combination of thecolor filter of Comparative Example 2 and a backlight source, acombination of the color filter of Comparative Example 4 and a backlightsource, and a combination of the color filter of Comparative Example 1and a backlight source, the combinations are equal in the colorreproducibility range with the transmissive region chromaticity andbrightness with the reflective region chromaticity. On the other hand,the rates of improvement in the range of color reproducibility withreflective region chromaticity of Comparative Examples 2 and 3 are 13%and 20%, respectively, as compared with that of Comparative Example 1.These rates of improvement are lower than that in the use of thethree-peak type LED light source. In comparison between the colorcharacteristics of a combination of the color filter of ComparativeExample 3 and a backlight source, a combination of the color filter ofComparative Examples 5 and a backlight source, and a combination of thecolor filter of Comparative Example 1 and a backlight source, thecombinations are equal in the color reproducibility range with thetransmissive region chromaticity and brightness with the reflectiveregion chromaticity. On the other hand, the rates of improvement inbrightness with the reflective region chromaticity of ComparativeExamples 2 and 3 are 3% and 5%, respectively, as compared with that ofComparative Example 1. These rates of improvement are lower than that inthe use of the three-peak type LED light source. These results arepossibly due to the fact that the three-peak type fluorescent lightsource used in Comparative Example 2 has relatively large side peaksnear 490 nm and 580 nm. It is also thought that the three-peak typeorganic EL light source used in Comparative Example 3 has a broad peakover the entire spectrum, and thus the improvement in the colorcharacteristics with the reflective region chromaticity is lowered.Therefore, it is found that the three-peak type LED of the three-peaktype light sources can significantly improve the color characteristicsof a reflective display of a transflective liquid crystal display.

Comparative Example 6

A color filter substrate having a conventional configuration was formedby the sa me method as in Example 1 except that a photomask having anaperture region ratio of zero was used for photolithography of red,green and blue picture elements so as to form reflective regions andtransmissive regions having the same color characteristics, as shown inFIG. 6. Then, an over coat layer and an ITO film were deposited on theresultant picture element film by the same method as in Example 1. Forthe thus-formed color filter substrate, the spectrum of each of thecentral picture element and the four corner picture elements of thesubstrate was measured. The measured spectra of the picture elementswere averaged.

Comparative Example 7

A color filter substrate having a conventional configuration was formedby the same method as in Comparative Example 1 except that a photomaskhaving an aperture region ratio of zero was used for photolithography ofred, green and blue picture elements so as to form reflective regionsand transmissive regions having the same color characteristics, as shownin FIG. 6. Then, an over coat layer and an ITO film were deposited onthe resultant picture element film by the same method as in Example 1.For the thus-formed color filter substrate, the spectrum of each of thecentral picture element and the four corner picture elements of thesubstrate was measured. The measured spectra of the picture elementswere averaged.

Table 5 shows the reflective region chromaticity of the colored filmsmeasured with light source D65 and the transmissive region chromaticitymeasured with a three-peak type LED light source (ultraviolet LED+RGBphosphors) in Comparative Example 6, and the reflective regionchromaticity of the colored films measured with light source D65 and thetransmissive region chromaticity measured with a two-peak type LED lightsource in Comparative Example 7.

TABLE 5 Transmissive region chromaticity Reflective region chromaticity(light source D65) Color re- Light Color repro- Brightness(Y x y Yproducibility source x y Y ducibility*1) value of W)*1) Comp. R 0.6180.294 32.4 60% Three-peak R 0.645 0.334 19.3 71% 26.8 (+25%) Example G0.271 0.596 62.0 type LED G 0.289 0.603 53.3 6 B 0.137 0.165 20.1(UV-LED + RGB B 0.135 0.090 7.7 W 0.336 0.341 38.2 phosphors) W 0.3210.348 26.8 Comp. R 0.630 0.349 23.4 60% Two-peak R 0.663 0.333 16.9 84%21.4 Example G 0.333 0.576 57.3 type LED G 0.261 0.638 42.6 7 B 0.1320.090 8.6 B 0.137 0.070 4.5 W 0.336 0.341 29.8 W 0.330 0.352 21.4*1)(Improvement over Comparative Example)

In comparison between the color characteristics of a combination of thecolor filter of Comparative Example 6 and a backlight source, and acombination of the color filter of Comparative Example 7 and a backlightsource, brightness with the reflective region chromaticity measured withthe three-peak type LED light source is 25% higher than that in the useof the two-peak type LED light source. Although an improvement inbrightness is high, the absolute value (Y value of white W) ofbrightness is only 26.8, and thus the color filter is very dark as acolor filter for a transflective liquid crystal display. Therefore, acombination of the three-peak type LED light source and the color filterhaving the conventional configuration cannot satisfy the characteristicsrequired for a transflective liquid crystal display. Therefore, it isfound that a color filter is required to have a configuration comprisingtransmissive regions and reflective regions having different colorcharacteristics.

Example 5

The non-photosensitive paste (TPI-1) was coated on a glass substratehaving a black matrix pattern formed thereon.

The coating film was dried at 120° C. for 20 minutes in an oven, andthen a positive photoresist (TOKYO OHKA KOGYO CO., LTD. OFPR-800) wascoated on the coating film and then dried at 90° C. for 10 minutes in anoven. The substrate was exposed with 60 mJ/cm² (strength of ultravioletlight at 365 nm) by Canon Inc. Proximity Exposure “PLA-501F” through aphotomask pattern to leave a transparent resin layer in a reflectiveregion of each of red, green and blue picture elements. After exposure,the substrate was dipped in a developer comprising a 1.6% aqueoussolution of tetramethylammonium hydroxide to simultaneously performdevelopment of the photoresist and etching of the polyamic acid coatingfilm. After etching, the unnecessary photoresist layer was removed withacetone, and the remaining layer was heat-treated at 240° C. for 30minutes to obtain the transparent resin layer in the reflective regionof each of the picture elements. The thickness of each transparent resinlayer was 1.8 μm.

Next, the red resist (RAC-1) was coated by a spinner on the glasssubstrate having the transparent resin layers, and then the resultantcoating film was heat-treated in an oven at 80° C. for 10 minutes. Thecoating film was then exposed with 100 mJ/cm² (strength of ultravioletlight at 365 nm) by an ultraviolet exposure apparatus through a chromiumphotomask for transmitting light through the transmissive regions andreflective regions of red picture elements. After exposure, thesubstrate was dipped in a developer comprising a 1.6% aqueous solutionof tetramethylammonium hydroxide to develop colored layers. Afterdevelopment, a heat treatment was performed in an oven at 240° C. for 30minutes to obtain the red picture elements. The thickness at the centerof the transmissive region of each picture element was 1.2 μm, and thechromaticity (x, y) with standard light source C was (0.567, 0.310). Thetotal thickness (the total thickness of the coating films of TPI-1 andRAC-1) at the center of the transmissive region of each red pictureelement was 2.3 μm, and the ratio of the thickness of the colored layerin each reflective region to that in each transmissive region was 2/5.

Similarly, the green resist (GAC-1) was coated by a spinner on the glasssubstrate to form a colored coating film. The coating thickness at thecenter of the transmissive region of each picture element was 1.2 μm,and the chromaticity (x, y) with standard light source C was (0.321,0.541). The total thickness (the total thickness of the coating films ofTPI-1 and GAC-1) at the center of the transmissive region of each greenpicture element was 2.3 μm, and the ratio of the thickness of thecolored layer in each reflective region to that in each transmissiveregion was 2/5.

Similarly, the blue resist (BAC-1) was coated by a spinner on the glasssubstrate to form a colored coating film. The coating thickness at thecenter of the transmissive region of each picture element was 1.2 μm,and the chromaticity (x, y) with standard light source C was (0.138,0.127). The total thickness (the total thickness of the coating films ofTPI-1 and BAC-1) at the center of the transmissive region of eachpicture element was 2.3 μm, and the ratio of the thickness of thecolored layer in each reflective region to that in each transmissiveregion was 2/5. Then, an over coat layer (JRS Corporation, “OptomerSS6500/SS0500”) was deposited to a thickness of 2 μm on the pictureelement layer formed as described above. Furthermore, an over coat layer(JRS Corporation, “Optomer SS6500/SS0500”) was deposited to a thicknessof 2 μm on the over coat layer, and an ITO film was deposited to athickness of 0.1 μm on the over coat layer by sputtering. For thethus-formed color filter substrate, the spectrum of each of the centralpicture element and the four corner picture elements of the substratewas measured. FIG. 10 shows a spectrum in a transmissive region, andFIG. 12 shows a spectrum in a reflective region.

Comparative Example 8

A transparent resin layer was coated, by the same method as in Example5, on a glass substrate having a black matrix pattern formed thereon.The thickness of the transparent resin layer was 2.6 μm.

Next, the red resist (RAC-1) was coated by a spinner on the glasssubstrate having the transparent resin layer to obtain red pictureelements in the same manner as in Example 5. The thickness at the centerof the transmissive region of each picture element was 1.8 μm, and thechromaticity (x, y) with standard light source C was (0.622, 0.328). Thetotal thickness (the total thickness of the coating films of TPI-1 andRAC-1) at the center of the transmissive region of each picture elementwas 3.4 μm, and the ratio of the thickness of the colored layer in eachreflective region to that in each transmissive region was 2/5.

Similarly, the green resist (GAC-1) was coated by a spinner on the glasssubstrate to form a colored coating film. The coating thickness at thecenter of the transmissive region of each picture element was 1.8 μm,and the chromaticity (x, y) with standard light source C was (0.298,0.581). The total thickness (the total thickness of the coating films ofTPI-1 and GAC-1) at the center of the transmissive region of eachpicture element was 3.4 μm, and the ratio of the thickness of thecolored layer in each reflective region to that in each transmissiveregion was 2/5.

Similarly, the blue resist (BAC-1) was coated by a spinner on the glasssubstrate to form a colored coating film. The coating thickness at thecenter of the transmissive,region of each picture element was 1.8 μm,and the chromaticity (x, y) with standard light source C was (0.135,0.099). The total thickness (the total thickness of the coating films ofTPI-1 and BAC-1) at the center of the transmissive region of eachpicture element was 3.4 μm, and the ratio of the thickness of thecolored-layer in each reflective region to that in each transmissiveregion was 2/5. Then, an over coat layer and an ITO film were depositedon the resulting picture element layer by the same method as in Example5. For the thus-formed color filter substrate, the spectrum of each ofthe central picture element and the four corner picture elements of thesubstrate was measured.

Table 6 shows the reflective region chromaticity of the colored coatingfilms measured with light source D65 and the transmissive regionchromaticity measured with a three-peak type LED light source(ultraviolet LED+RGB phosphors) in Example 5, and the reflective regionchromaticity of the colored coating films measured with light source D65and the transmissive region chromaticity measured with a two-peak typeLED light source in Comparative Example 8.

TABLE 6 Transmissive region chromaticity Reflective region chromaticity(light source D65) Color re- Light Color repro- Brightness(Y x y Yproducibility source x y Y ducibility*1) value of W)*1) Example R 0.6180.294 32.4 60% Three-peak R 0.537 0.305 27.5 38% 38.3 (+13%) 5 G 0.2710.596 62.0 type LED G 0.320 0.527 68.8 B 0.137 0.165 20.1 (UV-LED + RGBB 0.140 0.157 18.6 W 0.336 0.341 38.2 phosphors) W 0.315 0.339 38.3Comp. R 0.630 0.349 23.4 60% Two-peak R 0.599 0.321 24.1 55% 33.8Example G 0.333 0.576 57.3 type LED G 0.306 0.570 64.3 8 B 0.132 0.0908.6 B 0.135 0.122 13.0 W 0.336 0.341 29.8 W 0.319 0.344 33.8*1)(Improvement over Comparative Example)

In comparison between the color characteristics of a combination of thecolor filter of Example 5 and a backlight source and a combination ofthe color filter of Comparative Example 8 and a backlight source, bothcombinations are equal in the color reproducibility range with thetransmissive region chromaticity. However, white brightness withreflective region chromaticity in Example 5 is higher than that inComparative Example 8, and a reflective display with highervisibility,can be expected.

In comparison between the display characteristics of a liquid crystaldisplay comprising the color filter of Example 5 and a three-peak typeLED light source (ultraviolet LED+RGB phosphors) and a liquid crystaldisplay comprising the color filter of Comparative Example 8 and atwo-peak type LED light source, the liquid crystal display are equal inthe color vividness of a transmissive display. However, the liquidcrystal display of Comparative Example 8 exhibits insufficientbrightness and low visibility in a reflective display. On the otherhand, the liquid crystal display of Example 5 exhibits high brightnessand high visibility in a reflective display.

In this way, in a transflective liquid crystal display using a two-peaktype LED and a thickness-controlling system color filter in which thecolor reproducibility of a transmissive display is increased, areflective display with sufficient brightness cannot be achieved fromthe viewpoint of processing. However, in the use of a three-peak typeLED, a reflective display with sufficient brightness can be obtained.Namely, it can be said that a transmissive display with vividness and areflective display with sufficient brightness can be realized only by acombination of a three-peak type LED and a thickness-controlling systemcolor filter.

Example 6

A transparent resin layer was formed, by the same method as in Example5, in a portion corresponding to the reflective region of each of redand blue picture elements on a glass substrate having a black matrixpattern. The thickness of the transparent resin layers was 1.8 μm.

Next, the red resist (RAC-1) was coated by a spinner on the glasssubstrate having the transparent resin layers to obtain red pictureelements in the same manner as in Example 10. The thickness at thecenter of the transmissive region of each picture element was 1.2 μm,and the chromaticity (x, y) with standard light source C was (0.567,0.310). The total thickness (the total thickness of the coating films ofTPI-1 and RAC-1) at the center of the transmissive region of eachpicture element was 2.3 μm, and the ratio of the thickness of the,colored layer in each reflective region to that in each transmissiveregion was 2/5.

Similarly, the blue resist (BAC-1) was coated by a spinner on the glasssubstrate to form a colored coating film. The coating thickness at thecenter of the transmissive region of each picture element was 1.2 μm,and the chromaticity (x, y) with standard light source C was (0.138,0.127). The total thickness (the total thickness of the coating films ofTPI-1 and BAC-1) at the center of the transmissive region of eachpicture element was 2.3 μm, and the ratio of the thickness of thecolored layer in each reflective region to that in each transmissiveregion was 2/5.

Next, the green resist (GAC-1) was coated by a spinner in thetransmissive regions of green picture elements to form colored coatingfilms by the same method as in Example 5. The coating thickness at thecenter of the transmissive region of each picture element was 1.2 μm,and the chromaticity (x, y) with standard light source C was (0.321,0.541).

Next, the green resist (GAC-1) was further coated by a spinner in thetransmissive regions of the green picture elements to form coloredcoating films by the same method as in Example 5. The coating thicknessat the center of the transmissive region of each picture element was 1.2μm, and the chromaticity (x, y) with standard light source C was (0.321,0.541). Next, the green resist (GAC-2) was coated by a spinner in thereflective regions of the green picture elements to form colored coatingfilms by the same method as in Example 5. The coating thickness at thecenter of the reflective region of each picture element was 1.2 μm, andthe chromaticity (x, y) with standard light source C was (0.329, 0.444).

Then, an over coat layer and an ITO film were deposited on the resultingpicture element layer by the same method as in Example 5. For thethus-formed color filter substrate, the spectrum of each of the centralpicture element and the four corner picture elements of the substratewas measured.

Comparative Example 9

A transparent resin layer was formed, by the same method as in-Example5, on a glass substrate having a black matrix pattern formed thereon.The thickness of the transparent resin layer was 2.6 μm.

Next, the red resist (RAC-1) was coated by a spinner on the glasssubstrate having the transparent resin layer to obtain red pictureelements in the same manner as in Example 5. The thickness at the centerof the transmissive region of each picture element was 1.8 μm, and thechromaticity (x, y) with standard light source C was (0.622, 0.328). Thetotal thickness (the total thickness of the coating films of TPI-1 andRAC-1) at the center of the transmissive region of each picture elementwas 3.4 μm, and the ratio of the thickness of the colored layer in eachreflective region to that in each transmissive region was 2/5.

Similarly, the blue resist (BAC-1) was coated by a spinner on the glasssubstrate to form a colored coating film. The coating thickness at thecenter of the transmissive region of each picture element was 1.8 μm,and the chromaticity (x, y) with standard light source C was (0.135,0.099). The total thickness (the total thickness of the coating films ofTPI-1 and BAC-1) at the center of the transmissive region of eachpicture element was 3.4 μm, and the ratio of the thickness of thecolored layer in each reflective region to that in each transmissiveregion was 2/5.

Next, the green resist (GAC-1) was coated by a spinner in thetransmissive regions of green picture elements to form colored coatingfilms by the same method as in Example 5. The coating thickness at thecenter of the transmissive region of each picture element was 1.2 μm,and the chromaticity (x, y) with standard light source C was (0.321,0.541). Next, the green resist (GAC-2) was coated by a spinner in thereflective regions of the green picture elements to form colored coatingfilms by the same method as in Example 5. The coating thickness at thecenter of the reflective region of each picture element was 1.2 μm, andthe chromaticity (x, y) with standard light source C was (0.329, 0.444).

Then, an over coat layer and an ITO film were deposited on the resultingpicture element layer by the same method as in Example 5. For thethus-formed color filter substrate, the spectrum of each of the centralpicture element and the four corner picture elements of the substratewas measured.

Table 7 shows the reflective region chromaticity of the colored coatingfilms measured with light source D65 and the transmissive regionchromaticity measured with a three-peak type LED light source(ultraviolet LED+RGB phosphors) in Example 6, and the reflective regionchromaticity of the colored coating films measured with light source D65and the transmissive region chromaticity measured with a two-peak typeLED light source in Comparative Example 9.

TABLE 7 Transmissive region chromaticity Reflective region chromaticity(light source D65) Color re- Light Color repro- Brightness(Y x y Yproducibility source x y Y ducibility*1) value of W)*1) Example R 0.6180.294 32.4 60% Three-peak R 0.537 0.305 27.5 38% 38.9 (+8%) 6 G 0.2710.596 62.0 type LED G 0.322 0.527 70.6 B 0.137 0.165 20.1 (UV-LED + RGBB 0.140 0.157 18.6 W 0.336 0.341 38.2 phosphors) W 0.316 0.341 38.9Comp. R 0.630 0.349 23.4 60% Two-peak R 0.599 0.321 24.1 48% 35.9Example G 0.333 0.576 57.3 type LED G 0.322 0.527 70.6 9 B 0.132 0.0908.6 B 0.135 0.122 13.0 W 0.336 0.341 29.8 W 0.324 0.341 35.9*1)(Improvement over Comparative Example)

In comparison between the color characteristics of a combination of thecolor filter of Example 6 and a backlight source and a combination ofthe color filter of Comparative Example 9 and a backlight source, bothcombinations are equal in the color reproducibility range with thetransmissive region chromaticity and the color reproducibility rangewith the reflective region chromaticity. However, brightness of thereflective regions of Example 6 is 8% higher than that in ComparativeExample 9.

In comparison between the display characteristics of a liquid crystaldisplay comprising the color filter of Example 6 and a three-peak typeLED light source (ultraviolet LED+RGB phosphors) and a liquid crystaldisplay comprising the color filter of Comparative Example 9 and atwo-peak type LED light source, the liquid crystal displays are equal inthe color vividness of a transmissive display. However, the liquidcrystal display of Example 6 exhibits high brightness in a reflectivedisplay and high visibility even in the dark. On the other hand, theliquid crystal display of Comparative Example 9 produces a darkreflective display to make a display slightly hard to see.

In this way, in a transflective liquid crystal display using a two-peaktype LED and a color filter in which reflective regions and transmissiveregions of one of the colors have different coating characteristics, andthe transmissive regions and reflective regions of the other two colorsare formed in a thickness-controlling system, when the colorreproducibility of a transmissive display is increased, a reflectivedisplay with sufficient brightness cannot be achieved. However, in theuse of a three-peak type LED, a reflective display with sufficientbrightness can be obtained. Namely, it can be said that a transmissivedisplay with vividness and a reflective display with sufficientbrightness can be realized only by a combination of a three-peak typeLED and a color filter containing picture elements of at least one colorformed in a thickness-controlling system.

Example 7

A transparent resin layer was formed, by the same method as in Example5, on a glass substrate having a black matrix pattern formed thereon.The thickness of the transparent resin layer was 2.0 μm.

Next, the red resist (RAC-1) was coated by a spinner on the glasssubstrate having the transparent resin layer to obtain red pictureelements in-the same manner as in Example 5. The thickness at the centerof the transmissive region of each picture element was 1.4 μm, and thechromaticity (x, y) with standard light source C was (0.588, 0.316). Thetotal thickness (the total thickness of the coating films of tPI-1 andRAC-1) at the center of the transmissive region of each picture elementwas 2.6 μm, and the ratio of the thickness of the colored layer in eachreflective region to that in each transmissive region was 2/5.

Similarly, the green resist (GAC-1) was coated on the substrate to forma colored coating film by a spinner. The coating thickness at the centerof the transmissive region of each picture element was 1.4 μm, and thechromaticity (x, y) with standard light source C was (0.316, 0.554). Thetotal thickness (the total thickness of the coating films of TPI-1 andGAC-1) at the center of the transmissive region of each picture elementwas 2.6 μm, and the ratio of the thickness of the colored layer in eachreflective region to that in each transmissive region was 2/5.

Similarly, the blue resist (BAC-1) was coated on the glass substrate bya spinner to form a colored coating film. The coating thickness at thecenter of the transmissive region of each picture element was 1.4 μm,and the chromaticity (x, y) with standard light source C was (0.136,0.117). The total thickness (the total thickness of the coating films ofTPI-1 and BAC-1) at the center of the transmissive region of eachpicture element was 2.6 μm, and the ratio of the thickness of thecolored layer in each reflective region to that in each transmissiveregion was 2/5.

Then, an over coat layer and an ITO film were deposited on the resultingpicture element layer by the same method as in Example 5. For thethus-formed color filter substrate, the spectrum of each of the centralpicture element and the four corner picture elements of the substratewas measured.

Comparative Example 10

A transparent resin layer was formed, by the same method as in Example5, on a glass substrate having a black matrix pattern formed thereon.The thickness of the transparent resin layer was 3.2 μm. Next, the redresist (RAC-1) was coated by a spinner on the glass substrate having thetransparent resin layer to obtain red picture elements in the samemanner as in Example 5. The thickness at the center of the transmissiveregion of each picture element was 2.3 μm, and the chromaticity (x, y)with standard light source C was (0.644, 0.333). The total thickness(the total thickness of the coating films of TPI-1 and RAC-1) at thecenter of the transmissive region of each picture element was 4.1 μm,and the ratio of the thickness of the colored layer in each reflectiveregion to that in each transmissive region was 2/5.

Similarly, the green resist (GAC-1) was coated on the substrate by aspinner to form a colored coating film. The coating thickness at thecenter of the transmissive region of each picture element was 2.3 μm,and the chromaticity (x, y) with standard light source C was (0.287,0.601). The total thickness (the total thickness of the coating films ofTPI-1 and GAC-1) at the center of the transmissive region of eachpicture element was 4.1 μm, and the ratio of the thickness of thecolored layer in each reflective region to that in each transmissiveregion was 2/5.

Similarly, the blue resist (BAC-1) was coated on the glass substrate bya spinner to form a colored coating film. The coating thickness at thecenter of the transmissive region of each picture element was 2.3 μm,and the chromaticity (x, y) with standard light source C was (0.136,0.085). The total thickness (the total thickness of the coating films ofTPI-1 and BAC-1) at the center of the transmissive region of eachpicture element was 4.1 μm, and the ratio of the thickness of thecolored layer in each reflective region to that in each transmissiveregion was 2/5.

Then, an over coat layer and an ITO film were deposited on the resultingpicture element layer by the same method as in Example 5. For thethus-formed color filter substrate, the spectrum of each of the centralpicture element and the four corner picture elements of the substratewas measured.

Table 8 shows the reflective region chromaticity of the colored coatingfilms measured with light source D65 and the transmissive regionchromaticity measured with a three-peak type LED light source(ultraviolet LED+RGB phosphors) in Example 7, and the reflective regionchromaticity of the colored coating films measured with light source D65and the transmissive region chromaticity measured with a two-peak typeLED light source in Comparative Example 10.

TABLE 8 Transmissive region chromaticity Reflective region chromaticity(light source D65) Color re- Light Color repro- Brightness(Y x y Yproducibility source x y Y ducibility*1) value of W)*1) Example R 0.6340.298 31.0 68% Three-peak R 0.509 0.315 30.5 22% 42.2 (+28%) 7 G 0.2550.617 59.4 type LED G 0.314 0.435 74.3 B 0.137 0.151 17.5 (UV-LED + RGBB 0.166 0.175 21.7 W 0.336 0.341 36.0 phosphors) W 0.316 0.323 42.2Comp. R 0.644 0.349 21.1 68% Two-peak R 0.513 0.331 26.4 22% 33.0Example G 0.322 0.596 51.1 type LED G 0.295 0.437 57.5 10 B 0.133 0.0776.6 B 0.204 0.169 15.1 W 0.336 0.340 26.3 W 0.326 0.329 33.0*1)(Improvement over Comparative Example)

In comparison between the color characteristics of a combination of thecolor filter of Example 7 and a backlight source and a combination ofthe color filter of Comparative Example 10 and a backlight source, bothcombinations are equal in the color reproducibility range with thetransmissive region chromaticity and the color reproducibility rangewith the reflective region chromaticity. However, brightness of thereflective regions of Example 7 is 28% higher than that in ComparativeExample 10.

In comparison between the display characteristics of a liquid crystaldisplay comprising the color filter of Example 7 and a three-peak typeLED light source (ultraviolet LED+RGB phosphors) and a liquid crystaldisplay comprising the color filter of Comparative Example 10 and atwo-peak type LED light source, both liquid crystal displays are equalin the color vividness of a transmissive display. However, the liquidcrystal display of Example 7 exhibits high brightness in a reflectivedisplay and high visibility even in the dark. On the other hand, theliquid crystal display of Comparative Example 10 produces a darkreflective display to make a display hard to see.

In this way, in a transflective liquid crystal display using a two-peaktype LED and a color filter in which a thickness-controlling system andan area-controlling system are combined, when the color reproducibilityof a transmissive display is increased, a reflective display withsufficient brightness cannot be achieved. However, in the use of athree-peak type LED, a reflective display with sufficient brightness canbe obtained. Namely, it can be said that a transmissive display withvividness and a reflective display with sufficient brightness can berealized only by a combination of a three-peak type LED and a colorfilter in which the thickness-controlling system and thearea-controlling system are combined.

Comparative Example 11

The red resist (RAC-2), green resist (GAC-2) and blue resist (BAC-2)were coated in the reflective regions of red picture elements, greenpicture elements, and blue picture elements, respectively, on asubstrate by a spinner to form colored coating films in the same manneras in Example 5. The coating thickness at the center of the transmissiveregion of each of the red, green and blue picture elements was 1.2 μm,and the degrees of chromaticity (x, y) of the red, green and bluepicture elements with standard light source C were (0.453, 0.308),(0.329, 0.444), and (0.170, 0.205), respectively. Then, colored coatingfilms were formed in the respective transmissive regions of the red,green and blue picture elements by the same method as in Example 5.

Then, an over coat layer and an ITO film were deposited on the resultantpicture element film by the same method as in Example 1. For thethus-formed color filter substrate, the spectrum of each of the centralpicture element and the four corner picture elements of the substratewas measured. The measured spectra of the picture elements wereaveraged.

Comparative Example 12

Color coated layers were formed by the same method as in ComparativeExample 11 except that color coated layers were formed in the respectivetransmissive regions of red picture elements, and green picture elementsand blue picture elements by the same manner as in Comparative Example8.

Then, an over coat layer and an ITO film were deposited on the resultantpicture element film by the same method as in Example 1. For thethus-formed color filter substrate, the spectrum of each of the centralpicture element and the four corner picture elements of the substratewas measured. The measured spectra of the picture elements wereaveraged.

Table 9 shows the reflective region chromaticity of the colored coatingfilms measured with light source D65 and the transmissive regionchromaticity measured with a three-peak type LED light source(ultraviolet LED+RGB phosphors) in Comparative Example 11, and thereflective region chromaticity of the colored coating films measuredwith light source D65 and the transmissive region chromaticity measuredwith a two-peak type LED light source in Comparative Example 12.

TABLE 9 Transmissive region chromaticity Reflective region chromaticity(light source D65) Color re- Light Color repro- Brightness(Y x y Yproducibility source x y Y ducibility*1) value of W)*1) Comp. R 0.6180.294 32.4 60% Three-peak R 0.573 0.328 25.7 41% 38.4 (0%) Example G0.271 0.596 62.0 type LED G 0.322 0.527 70.6 11 B 0.137 0.165 20.1(UV-LED + RGB B 0.139 0.159 18.9 W 0.336 0.341 38.2 phosphors) W 0.3150.348 38.4 Comp. R 0.630 0.349 23.4 60% Two-peak R 0.573 0.328 25.7 41%38.4 Example G 0.333 0.576 57.3 type LED G 0.322 0.527 70.6 12 B 0.1320.090 8.6 B 0.139 0.159 18.9 W 0.336 0.341 29.8 W 0.315 0.348 38.4*1)(Improvement over Comparative Example)

In comparison between the color characteristics of a combination of thecolor filter of Comparative Example 11 and a backlight source and acombination of the color filter of Comparative Example 12 and abacklight source, both combinations are equal in the colorreproducibility range with the transmissive region chromaticity, and arethe same in characteristics with the reflective region chromaticity.

In comparison between the display characteristics of a liquid crystaldisplay comprising the color filter of Comparative Example 11 and athree-peak type LED light source (ultraviolet LED+RGB phosphors) and aliquid crystal display comprising the color filter of ComparativeExample 12 and a two-peak type LED light source, both liquid crystaldisplay are equal in the color vividness of a transmissive displays.Also, the liquid crystal displays of Comparative Examples 11 and 12 arethe same in characteristics of a reflective display.

In this way, in a six-color coating system, the colored coating films inthe transmissive regions are formed independently of those in thereflective regions, and thus a change of the backlight source causes noeffect of improving the characteristics of the reflective display.

Table 10 shows the effect of improving the brightness of a reflectivedisplay in each of the above-described liquid crystal displays of thepresent invention.

TABLE 10 UV-LED + RGB Organic Cold- RGB-LED phosphors EL cathode tubeArea control ◯ ◯ Δ Δ 15% 12% 5% 3% Thickness control ◯ 13% Six-colorcoating X  0%

This table indicates that even in a reflective display usingenvironmental light, brightness is improved by a combination of thearea-controlling system or thickness-controlling system color filter anda three-peak type backlight source. It is also found that brightness isimproved particularly when a LED light source among the three-peak typelight sources is used.

Example 8

The red paste (R-1) was coated by a spinner on a glass substrate havinga black matrix pattern formed thereon so that the chromaticity (x, y)measured by passing light of standard light source C through the glasssubstrate was (0.466, 0.294). The resultant coating film was dried at120° C. for 20 minutes, and then a positive photoresist (TOKYO OHKAKOUGYO CO., LTD. “OFPR-800”) was coated on the coating film and dried at90° C. for 10 minutes. The coating film was then exposed to light byusing Canon Inc. “Proximity Exposure PLA-501F” through a chromiumphotomask with a strength of 60 mJ/cm² (strength of ultraviolet light at365 nm). The photomask used had an aperture ratio (aperture regionratio) of 12% in reflective regions. After exposure, the substrate wasdipped in a developer comprising a 2.25% aqueous solution oftetramethylammonium hydroxide to simultaneously perform development ofthe photoresist and etching of the colored film of polyimide precursor.After etching, the unnecessary photoresist layer was removed withacetone. Furthermore, the colored film of polyamide precursor washeat-treated at 240° C. for 30 minutes to convert the polyamideprecursor to polyimide. Next, the blue paste (B-1) was coated so thatthe final chromaticity (x, y) measured by passing light of standardlight source C through the glass substrate was (0.152, 0.190), and thenphotolithography was performed by the same method as that used for thered picture elements. The photomask used had an aperture ratio (apertureregion ratio) of 9% in the reflective regions. Next, the color paste(G-1) was coated by a spinner so that the final chromaticity (x, y)measured by passing light of standard light source C through the glasssubstrate was (0.309, 0.373), and then photolithography was performed bythe same method as that used for the red picture elements. The photomaskused for green picture elements had an aperture region ratio of zero.Finally, the color paste (G-2) was coated by a spinner to laminate greencolored layers in the transmissive regions of the green pictureelements. The chromaticity (x, y) of the transmissive regions of thegreen picture elements, which was measured by using standard lightsource C, was (0.284, 0.443). Then, an over coat layer was deposited toa thickness of 2 μm on the thus-obtained picture element layer, and anITO film was deposited to a thickness of 0.1 μm by sputtering on theover coat layer. For the thus-obtained color filter substrate, thespectrum of each of the central picture element and the four cornerpicture elements of the substrate was measured. Table 11 shows thereflective region chromaticity measured with light source D65, thetransmissive region chromaticity measured with a two-peak type LED lightsource, and chromaticity difference δ of the resultant color filter.

TABLE 11 Transmissive region Reflective region chromaticity (two-peakchromaticity (light source type LED light source) D65) Chromaticity x yY x y Y difference δ R 0.489 0.332 42.6 0.485 0.331 33.1 1.7 × 10⁻⁵ G0.307 0.438 68.7 0.308 0.438 67.9 1.5 × 10⁻⁷ B 0.154 0.186 26.1 0.1680.185 21.6 1.9 × 10⁻⁴

Comparative Example 13

A color filter was formed by the same method as in Example 8 except thata photomask producing no aperture region in each picture element wasused for photolithography of red, blue and green picture elements, eachgreen picture element was not formed by laminating, and the finalchromaticity measured by passing light of standard light source C wasdifferent from that in Example 8. In this comparative example, the redpaste (R-1), green paste (G-1) and blue paste (B-1) were used. Thedegrees of chromaticity (x, y) of the red picture elements, the greenpicture elements, and the blue picture elements, which were measured bypassing light of standard light source C, were (0.405, 0.285), (0.309,0.373), and (0.178, 0.225), respectively.

For the thus-formed color filter substrate, the spectrum of each of thecentral picture element and the four corner picture elements of thesubstrate was measured. The measured spectra of the picture elementswere averaged. Table 12 shows the reflective region chromaticitymeasured with light source D65, the transmissive region chromaticitymeasured with a two-peak type LED light source, and chromaticitydifference δ of the resultant color filter.

TABLE 12 Transmissive region Reflective region chromaticity (two-peakchromaticity (light type LED light source) source D65) Chromaticity x yY x y Y difference δ R 0.425 0.317 54.0 0.486 0.304 32.6 3.9 × 10⁻³ G0.328 0.379 86.0 0.308 0.438 67.9 3.8 × 10⁻³ B 0.184 0.227 36.8 0.1430.187 22.3 3.3 × 10⁻³

Comparative Example 14

A color filter was formed by the same method as in Example 8 except thata photomask patterned to produce an aperture region ratio of 26% in eachgreen element was use for photolithography of the green pictureelements, green paste was coated so that the final chromaticity measuredby passing light of standard light source C was (0.303, 0.440), and thegreen picture elements were not formed by laminating the paste. The redpaste (R-1), green paste (G-1) and blue paste (B-1) were used.

For the thus-formed color filter substrate, the spectrum of each of thecentral picture element and the four corner picture elements of thesubstrate was measured. The measured spectra of the picture elementswere averaged. Table 13 shows the reflective region chromaticitymeasured with light source D65, the transmissive region chromaticitymeasured with a two-peak type LED light source, and chromaticitydifference δ of the resultant color filter.

TABLE 13 Transmissive region Reflective region chromaticity (two-peakchromaticity (light type LED light source) source D65) Chromaticity x yY x y Y difference δ R 0.489 0.332 42.6 0.485 0.331 33.1 1.7 × 10⁻⁵ G0.326 0.437 74.2 0.300 0.438 62.3 6.6 × 10⁻⁴ B 0.154 0.186 26.1 0.1680.185 21.6 1.9 × 10⁻⁴

The display characteristics of a transflective liquid crystal displaycomprising the color filter of each of Comparative Examples 13 and 14were compared with the characteristics of a liquid crystal displaycomprising the color filter of Example 8 under a condition in whichoutdoor environmental light was used in a reflective display with thebacklight source turned off, and the backlight source was turned on in atransmissive display in the dark. In the transmissive display, atwo-peak type LED light source was used as a light source. The liquidcrystal display manufactured by a conventional technique in ComparativeExample 1 exhibited a light color over the entire transmissive displayand a great difference in visibility from the reflective display. On theother hand, the liquid crystal display using the color filter of Example8 had substantially no color difference between the reflective displayand the transmissive display, and thus exhibited good displaycharacteristics. The liquid crystal display of Comparative Example 14exhibited good colors in the reflective display and the transmissivedisplay, as compared with Comparative Example 13. However, a slightchange in coloring was observed between the liquid crystal displays ofComparative Example 14 and Example 8, and the brightness of thereflective display of Comparative Example 14 was lower than that ofExample 8.

Example 9

The red paste (R-2) was coated by a spinner on a glass substrate havinga black matrix pattern formed thereon, the red paste being controlled tothe ratio shown in Table 1 so that the chromaticity (x, y) measured bypassing light of standard light source C through the glass substrate was(0.405, 0.301). The resultant coating film was dried at 120° C. for 20minutes, and then a positive photoresist (TOKYO OHKA KOUGYO CO., LTD.“OFPR-800”) was coated on the coating film and dried at 90° C. for 10minutes. The coating film was then exposed to light by using Canon Inc.“Proximity Exposure “PLA-501F” through a chromium photomask with astrength of 60 mJ/cm² (strength of ultraviolet light at 365 nm) aphotomask producing an aperture region ratio of zero in red pictureelements was used. After exposure, the substrate was dipped in adeveloper comprising a 2.25% aqueous solution of tetramethylammoniumhydroxide to simultaneously perform development of the photoresist andetching of the colored film of polyimide precursor. After etching, theunnecessary photoresist layer was removed with acetone. Furthermore, thecolored film of polyamide precursor was heat-treated at 240° C. for 30minutes to convert the polyamide precursor to polyimide. Next, the colorpaste (G-1) was coated by a spinner so that the final chromaticity (x,y) measured by passing light of standard light source C was (0.307,0.426), and then photolithography was performed by the same method asthat used for the red picture elements. The photomask used had anaperture ratio (aperture region ratio) of 23% in the reflective regions.Next, the color paste (B-1) was coated so that the chromaticity (x, y)measured by passing light of standard light source C through the glasssubstrate was (0.148, 0.182), and then photolithography was performed bythe same method as that used for the red picture elements. The photomaskused had an aperture ratio (aperture region ratio) of 10% in thereflective regions. Finally, the color paste (R-3) controlled to theratio shown in Table 1 was coated by a spinner to laminate a red coloredlayer over the entire transmissive regions of the red picture elementsand in a 50% area of the transmissive regions of each blue pictureelement. The chromaticity (x, y) of the transmissive regions of the redpicture elements, which was measured by using standard light source C,was (0.474, 0.326). The chromaticity (x, y) of the transmissive regionsof the blue picture elements, which was measured by using standard lightsource C, was (0.171, 0.169). Then, an over coat layer was deposited toa thickness of 2 μm on the thus-obtained picture element layer, and anITO film was deposited to a thickness of 0.1 μm by sputtering on theover coat layer.

For the thus-obtained color filter substrate, the spectrum of each ofthe central picture element and the four corner picture elements of thesubstrate was measured. The measured spectra of the picture elementswere averaged. Table 14 shows the reflective region chromaticitymeasured with light source D65, the transmissive region chromaticitymeasured with a three-peak type LED light source (RGB chip LEDs), andchromaticity difference δ of the resultant color filter.

TABLE 14 Transmissive region Reflective region chromaticity (three-peakchromaticity (light type LED light source) source D65) Chromaticity x yY x y Y difference δ R 0.488 0.321 41.1 0.488 0.323 33.4 2.9 × 10⁻⁶ G0.298 0.438 74.5 0.305 0.438 61.4 4.9 × 10⁻⁵ B 0.169 0.186 21.4 0.1740.187 20.9 3.2 × 10⁻⁵

Comparative Example 15

In forming a color filter, a photomask having a pattern for producing anaperture region ratio of 11% in each red element was used forphotolithography of red picture elements, and a photomask having apattern for producing an aperture region ratio of 12% in each blueelement was used in photolithography for blue picture elements. In thiscomparative example, the red paste (R-2), green paste (G-1) and bluepaste (B-1) were used. Each of the red picture elements and blue pictureelements was not formed by laminating the paste. The degrees ofchromaticity (x, y) of the red picture elements and the blue pictureelements, which were measured by passing light of standard light sourceC, were (0.469, 0.313) and (0.141, 0.167), respectively. For the greenpicture elements, the green paste was coated and processed by the samemethod as in Example 9.

For the thus-formed color filter substrate, the spectrum of each of thecentral picture element and the four corner picture elements of thesubstrate was measured. The measured spectra of the picture elementswere averaged. Table 15 shows the reflective region chromaticitymeasured with light source D65, the transmissive region chromaticitymeasured with a three-peak type LED light source (RGB chip LEDs), andchromaticity difference δ of the resultant color filter.

TABLE 15 Transmissive region Reflective region chromaticity (three-peakchromaticity (light type LED light source) source D65) Chromaticity x yY x y Y difference δ R 0.488 0.308 36.8 0.488 0.344 31.0 1.2 × 10⁻³ G0.298 0.438 74.5 0.305 0.438 61.4 4.9 × 10⁻⁵ B 0.139 0.187 24.8 0.1830.187 20.1 1.9 × 10⁻³

The display characteristics of a transflective liquid crystal displaycomprising the color filter of Comparative Example 15 were compared withthe characteristics of a liquid crystal display comprising the colorfilter of Example 9 under a condition in which outdoor environmentallight was used in a reflective display with the backlight source turnedoff, and the backlight source was turned on in a transmissive display inthe dark. In the transmissive display, a three-peak type LED lightsource (RGB chip LEDs) was used as a light source. The liquid crystaldisplay using the color filter of Comparative Example 15 and the liquidcrystal display of Example 9 exhibited the same color vividness.However, the liquid crystal display using the color filter of Example 9had substantially no color difference between the reflective display andthe transmissive display, and thus exhibited good displaycharacteristics.

Example 10

The red paste (R-1) was coated by a spinner on a glass substrate havinga black matrix pattern formed thereon so that the chromaticity (x, y)measured by passing light of standard light source C through the glasssubstrate was (0.466, 0.294). The resultant coating film was dried at120° C. for 20 minutes, and then a positive photoresist (TOKYO OHKAKOUGYO CO., LTD. “OFPR-800”) was coated on the coating film and dried at90° C. for 10 minutes. The coating film was then exposed to light byusing Canon Inc. “Proximity Exposure “PLA-501F” through a chromiumphotomask with a strength of 60 mJ/cm² (strength of ultraviolet light at365 nm). The photomask used had an aperture ration (aperture regionratio) of 12% in reflective regions. After exposure, the substrate wasdipped in a developer comprising a 2.25% aqueous solution oftetramethylammonium hydroxide to simultaneously perform development ofthe photoresist and etching of the colored film of polyimide precursor.After etching, the unnecessary photoresist layer was removed withacetone. Furthermore, the colored film of polyamide precursor washeat-treated at 240° C. for 30 minutes to convert the polyamideprecursor to polyimide. Next, the blue paste (B-2) was coated so thatthe final chromaticity (x, y) measured by passing light of standardlight source C through the glass substrate was (0.200, 0.232), and thenphotolithography was performed by the same method as that used for thered picture elements a photomask producing no aperture region in theblue picture elements was used. Next, the color paste (G-1) was coatedby a spinner so that the chromaticity (x, y) measured by passing lightof standard light source C through the glass substrate was (0.309,0.373), and then photolithography was performed by the same method asthat used for the red picture elements. A photomask producing noaperture region in the green picture elements was used. Next, the colorpaste (G-2) was coated by a spinner to laminate a green colored layer onthe transmissive region of each green picture element. The chromaticity(x, y) measured by passing light of standard light source C through thetransmissive regions of the green picture elements was (0.284, 0.443).Finally, the color paste (B-1) was coated by a spinner to laminate ablue colored layer in the transmissive region of each blue pictureelements. The chromaticity (x, y) measured by using standard lightsource C through the transmissive regions of the blue picture elementswas (0.158, 0.188). Then, an over coat layer was deposited to athickness of 2 μm on the thus-obtained picture element layer, and an ITOfilm was deposited to a thickness of 0.1 μm by sputtering on the overcoat layer.

For the thus-obtained color filter substrate, the spectrum of each ofthe central picture element and the four corner picture elements of thesubstrate was measured. The measured spectra of the picture elementswere averaged. Table 16 shows the reflective region chromaticitymeasured with light source D65, the transmissive region chromaticitymeasured with a two-peak type LED light source, and chromaticitydifference δ of the resultant color filter.

TABLE 16 Transmissive region Reflective region chromaticity (two-peakchromaticity (light type LED light source) source D65) Chromaticity x yY x y Y difference δ R 0.489 0.332 42.6 0.485 0.331 33.1 1.7 × 10⁻⁵ G0.307 0.438 68.7 0.308 0.438 67.9 1.5 × 10⁻⁷ B 0.160 0.187 25.2 0.1550.186 22.1 3.0 × 10⁻⁵

The display characteristics of a transflective liquid crystal displaycomprising the color filter of Comparative Example 14 were compared withthe characteristics of a liquid crystal display comprising the colorfilter of Example 10 under a condition in which outdoor environmentallight was used in a reflective display with the backlight source turnedoff, and the backlight source was turned on in a transmissive display inthe dark. In the transmissive display, a two-peak type LED light sourcewas used as a light source. The liquid crystal display of Example 10 hadsubstantially no color difference between the reflective display and thetransmissive display, and thus exhibited good display characteristics.However, a slight change in coloring was observed between the liquidcrystal displays of Comparative Example 14 and Example 10, and thebrightness of the reflective display of Comparative Example 14 was lowerthan that of Example 10.

Example 11

The red paste (R-4) was coated by a spinner on a glass substrate havinga black matrix pattern formed thereon. The resultant coating film wasdried at 120° C. for 20 minutes, and then a positive photoresist (TOKYOOHKA KOUGYO CO., LTD. “OFPR-800”) was coated on the coating film anddried at 90° C. for 10 minutes. The coating film was then exposed tolight by using Canon Inc. “Proximity Exposure “PLA-501F” through achromium photomask with a strength of 60 mJ/cm² (strength of ultravioletlight at 365 nm). In this example, a photomask leaving a colored layeronly in the transmissive region of each red picture element was usedafter exposure, the substrate was dipped in a developer comprising a2.25% aqueous solution of tetramethylammonium hydroxide tosimultaneously perform development of the photoresist and etching of thecolored film of polyimide precursor. After etching, the unnecessaryphotoresist layer was removed with acetone. Furthermore, the coloredfilm of polyamide precursor was heat-treated at 240° C. for 30 minutesto convert the polyamide precursor to polyimide. The thickness of eachcolored layer was 1.4 μm, and the chromaticity measured by passing lightof standard light source C was (0.429, 0.281). Next, green pictureelements and blue picture elements were formed by the same method asthat used for the red picture elements. In this case, the green pate G-3and the blue paste B-3 were used. The thickness of each green coloredlayer was 1.4 μm, and the chromaticity measured by passing light ofstandard light source C was (0.291, 0.457). The thickness of each bluecolored layer was 1.4 μm, and the chromaticity measured by passing lightof standard light source C was (0.191, 0.241). As a result, thetransmissive regions were formed.

Next, colored layer patterns were formed in the transmissive regions andthe reflective regions by the same method as that for forming thetransmissive regions except that a photomask leaving color layers in thetransmissive regions and the reflective regions was used, and the colorpastes below were used. As a result, two-color layers were laminated ineach of the transmissive regions. In this case, the color paste R-6, thecolor paste G-5 and the blue paste B-5 were used for the red, green andblue picture elements, respectively. The thickness of the colored layerof the reflective region of each picture element was 1.4 μm. The degreesof chromaticity (x, y) of the red, green blue picture elements, whichwere measured by passing light of standard light source C, were (0.453,0.308), (0.329, 0.444), and (0.170, 0.205), respectively.

Then, an over coat layer was deposited to a thickness of 2 μm on thethus-obtained picture element layer, and an ITO film was deposited to athickness of 0.1 μm by sputtering on the over coat layer.

For the thus-obtained color filter substrate, the spectrum of each ofthe central picture element and the four corner picture elements of thesubstrate was measured. The measured spectra of the picture elementswere averaged. Table 17 shows the reflective region chromaticitymeasured with light source D65, the transmissive region chromaticitymeasured with a three-peak type LED light source, and chromaticitydifference δ of the resultant color filter.

TABLE 17 Transmissive region Reflective region chromaticity (two-peakchromaticity (light type LED light source) source D65) Chromaticity x yY x y Y difference δ R 0.574 0.338 28.5 0.573 0.328 25.7 1.0 × 10⁻⁴ G0.321 0.527 58.8 0.322 0.527 70.6 1.1 × 10⁻⁶ B 6.143 0.159 20.0 0.1390.159 18.9 1.3 × 10⁻⁵

Example 12

The transmissive regions and reflective regions were first formed, andthen the transmissive regions were further formed. Namely, colored layerpatterns were formed by the same method as in Example 11 except that theorder of picture element formation was opposite to that in Example 11.

Then, an over coat layer was deposited to a thickness of 2 μm on thethus-obtained picture element layer, and an ITO film was deposited to athickness of 0.1 μm by sputtering on the over coat layer.

For the thus-obtained color filter substrate, the spectrum of each ofthe central picture element and the four corner picture elements of thesubstrate was measured. The measured spectra of the picture elementswere averaged. Table 18 shows the reflective region chromaticitymeasured with light source D65, the transmissive region chromaticitymeasured with a three-peak type LED light source, and chromaticitydifference δ of the resultant color filter.

TABLE 18 Transmissive region Reflective region chromaticity (two-peakchromaticity (light type LED light source) source D65) Chromaticity x yY x y Y difference δ R 0.574 0.338 28.5 0.573 0.328 25.7 1.0 × 10⁻⁴ G0.321 0.527 58.8 0.322 0.527 70.6 1.1 × 10⁻⁶ B 0.143 0.159 20.0 0.1390.159 18.9 1.3 × 10⁻⁵

Comparative Example 16

Colored layer patterns were formed in the transmissive regions by thesame method as in Example 11 except that the color pastes below wereused. In this comparative example, the red paste R-5, green paste G-4and blue paste B-4 were used. The thickness of the colored layer in thetransmissive region of each picture element was 1.4 μm. The degrees ofchromaticity (x, y) of the red picture elements, the green pictureelements, and the blue picture elements, which were measured by passinglight of standard light source C, were (0.552, 0.306), (0.298, 0.538),and (0.139, 0.159), respectively.

Next, colored layer patterns were formed in the reflective regions bythe same method as the above method used for forming the transmissiveregions except that a photomask leaving a colored layer only in eachreflective region, and the color pastes below were used. In thiscomparative example, the red paste R-6, green paste G-5 and blue pasteB-5 were used. The thickness of the colored layer in the transmissiveregion of each picture element was 1.4 μm. The degrees of chromaticity(x, y) of the red picture elements, the green picture elements, and theblue picture elements, which were measured by passing light of standardlight source C, were (0.453, 0.308), (0.329, 0.444), and (0.170, 0.205),respectively.

Then, an over coat layer was deposited to a thickness of 2 μm on thethus-obtained picture element layer, and an ITO film was deposited to athickness of 0.1 μm by sputtering on the over coat layer.

For the thus-formed color filter substrate, the spectrum of each of thecentral picture element and the four corner picture elements of thesubstrate was measured. The measured spectra of the picture elementswere averaged. Table 19 shows the reflective region chromaticitymeasured with light source D65, the transmissive region chromaticitymeasured with a three-peak type LED light source, and chromaticitydifference δ of the resultant color filter.

TABLE 19 Transmissive region Reflective region chromaticity (two-peakchromaticity (light type LED light source) source D65) Chromaticity x yY x y Y difference δ R 0.574 0.337 28.1 0.573 0.328 25.7 7.8 × 10⁻⁵ G0.328 0.530 61.2 0.322 0.527 70.6 5.8 × 10⁻⁵ B 0.139 0.150 18.6 0.1390.159 18.9 7.5 × 10⁻⁵

The display characteristics of a transflective liquid crystal displaycomprising the color filter of Comparative Example 16 were compared withthe characteristics of a liquid crystal display comprising the colorfilter of each of Examples 11 and 12 under a condition in which outdoorenvironmental light was used in a reflective display with the backlightsource turned off, and the backlight source was turned on in atransmissive display in the dark. In the transmissive display, atwo-peak type LED light source was used as a light source. The liquidcrystal display of each of Examples 11 and 12 had no color differencebetween the reflective display and the transmissive display, and thusexhibited good display characteristics. Although the liquid crystaldisplay of Comparative Example 16 had no color difference between thereflective display and the transmissive display, several whiteluminescent spots and color ununiformity were observed on a screen.Therefore, the liquid crystal display of Comparative Example 16 had lowimage quality.

INDUSTRIAL APPLICABILITY

The present invention can provide a low-cost transflective liquidcrystal display exhibiting high color reproducibility in a transmissivedisplay and excellent characteristics (color reproducibility andbrightness) in a reflective display. Also, a color filter for a brighttransflective liquid crystal display capable of producing a smallchromaticity difference between a reflective display and a transmissivedisplay can be realized.

1. A transflective liquid crystal display comprising a pair ofsubstrates disposed opposite to each other with a liquid crystal layerheld between the pair of substrates, a reflection means using ambientlight as a light source, a backlight source, and a color filter having atransmissive region and a reflective region which are provided in eachpicture element of the color filter and which have colored layerscomprising a single material, a three-peak type LED backlight sourcebeing used as the backlight source, wherein the color filter includesthe picture elements of at least one color in each of which the coloredlayers of the transmissive region and the reflective region have thesame thickness, and an aperture is formed in the reflective region, andwherein a color reproducibility of transmissive region chromaticity is60% or mores, a color reproducibility of reflective region chromaticityis 15% to 38%, and a brightness of reflective region chromaticity is36.9 or more.
 2. The transflective liquid crystal display according toclaim 1, wherein the x value of the transmissive region chromaticity ofthe red picture elements by using three-peak type LED backlight sourcesatisfying the following relation, x≧0.618.
 3. The transflective liquidcrystal display according to claim 1, wherein the y value of thetransmissive region chromaticity of the green picture elements by usingthree-peak type LED backlight source satisfying the following relation,y≧0.574.
 4. A transflective liquid crystal display comprising a pair ofsubstrates disposed opposite to each other with a liquid crystal layerheld between the pair of substrates, a reflection means using ambientlight as a light source, a backlight source, and a color filter having atransmissive region and a reflective region which are provided in eachpicture element of the color filter and which have colored layerscomprising a single material, a three-peak type LED backlight sourcebeing used as the backlight source, wherein the color filter includesthe picture elements of at least one color in each of which the coloredlayers of the reflective region, the transmissive region have differentthicknesses, and the color filter has the aperture formed in each of thereflective regions, and wherein a color reproducibility of transmissiveregion chromaticity is 60% or more, a color reproducibility ofreflective region chromaticity is 15% to 38%, and a brightness ofreflective region chromaticity is 36.9 or more.
 5. The transflectiveliquid crystal display according to claim 4, wherein the x value of thetransmissive region chromaticity of the red picture elements by usingthree-peak type LED backlight source satisfying the following relation,x≧0.618.
 6. The transflective liquid crystal display according to claim4, wherein the y value of the transmissive region chromaticity of thegreen picture elements by using three-peak type LED backlight sourcesatisfying the following relation, y≧0.574.